<PAGE>   1
                                                                    Exhibit 24.1

                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

         THAT I, Dr. Rolf-E. Breuer, a director of Cornerstone Properties Inc.
(the "Company"), do hereby constitute and appoint John S. Moody and Thomas P.
Loftus, and each of them, my true and lawful attorneys-in-fact and agents, to do
any and all acts and things and to execute any and all instruments which said
attorney and agent may deem necessary or advisable to enable the Company to
comply with the Securities Exchange Act of 1934, as amended, and any rules,
regulations and requirements of the Securities and Exchange Commission in
respect thereof, in connection with the filing under the said Securities
Exchange Act of the Company's Annual Report on Form 10-K for the fiscal year
ended December 31, 1996 (the "Annual Report"), including specifically, but
without limiting the generality of the foregoing, the power and authority to
sign for, on behalf of and in the name of the undersigned as a director of the
Company, such Annual Report and any amendments thereto filed with the Securities
and Exchange Commission and any instrument or document filed as part of, an
exhibit to, or in connection with said Annual Report or amendments thereto; and
the undersigned does hereby ratify and confirm as his own act and deed all that
said attorneys-in-fact and agents shall do or cause to be done by virtue hereof.

         IN WITNESS WHEREOF, the undersigned has subscribed these presents,
effective as of the 21st day of February, 1997.


                                                       /s/ Rolf-E. Breuer
                                                       -------------------------
                                                       Dr. Rolf-E. Breuer
<PAGE>   2
                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

         THAT I, Cecil D. Conlee, a director of Cornerstone Properties Inc. (the
"Company"), do hereby constitute and appoint John S. Moody and Thomas P. Loftus,
and each of them, my true and lawful attorneys-in-fact and agents, to do any and
all acts and things and to execute any and all instruments which said attorney
and agent may deem necessary or advisable to enable the Company to comply with
the Securities Exchange Act of 1934, as amended, and any rules, regulations and
requirements of the Securities and Exchange Commission in respect thereof, in
connection with the filing under the said Securities Exchange Act of the
Company's Annual Report on Form 10-K for the fiscal year ended December 31, 1996
(the "Annual Report"), including specifically, but without limiting the
generality of the foregoing, the power and authority to sign for, on behalf of
and in the name of the undersigned as a director of the Company, such Annual
Report and any amendments thereto filed with the Securities and Exchange
Commission and any instrument or document filed as part of, an exhibit to, or in
connection with said Annual Report or amendments thereto; and the undersigned
does hereby ratify and confirm as his own act and deed all that said
attorneys-in-fact and agents shall do or cause to be done by virtue hereof.

         IN WITNESS WHEREOF, the undersigned has subscribed these presents,
effective as of the 21st day of February, 1997.


                                                      /s/ Cecil D. Conlee
                                                      -------------------------
                                                      Cecil D. Conlee
<PAGE>   3
                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

         THAT I, George Abbott Davis, a director of Cornerstone Properties Inc.
(the "Company"), do hereby constitute and appoint John S. Moody and Thomas P.
Loftus, and each of them, my true and lawful attorneys-in-fact and agents, to do
any and all acts and things and to execute any and all instruments which said
attorney and agent may deem necessary or advisable to enable the Company to
comply with the Securities Exchange Act of 1934, as amended, and any rules,
regulations and requirements of the Securities and Exchange Commission in
respect thereof, in connection with the filing under the said Securities
Exchange Act of the Company's Annual Report on Form 10-K for the fiscal year
ended December 31, 1996 (the "Annual Report"), including specifically, but
without limiting the generality of the foregoing, the power and authority to
sign for, on behalf of and in the name of the undersigned as a director of the
Company, such Annual Report and any amendments thereto filed with the Securities
and Exchange Commission and any instrument or document filed as part of, an
exhibit to, or in connection with said Annual Report or amendments thereto; and
the undersigned does hereby ratify and confirm as his own act and deed all that
said attorneys-in-fact and agents shall do or cause to be done by virtue hereof.

         IN WITNESS WHEREOF, the undersigned has subscribed these presents,
effective as of the 21st day of February, 1997.


                                                   /s/ George Abbott Davis
                                                   -------------------------
                                                   George Abbott Davis
<PAGE>   4
                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

         THAT I, Blake Eagle, a director of Cornerstone Properties Inc. (the
"Company"), do hereby constitute and appoint John S. Moody and Thomas P. Loftus,
and each of them, my true and lawful attorneys-in-fact and agents, to do any and
all acts and things and to execute any and all instruments which said attorney
and agent may deem necessary or advisable to enable the Company to comply with
the Securities Exchange Act of 1934, as amended, and any rules, regulations and
requirements of the Securities and Exchange Commission in respect thereof, in
connection with the filing under the said Securities Exchange Act of the
Company's Annual Report on Form 10-K for the fiscal year ended December 31, 1996
(the "Annual Report"), including specifically, but without limiting the
generality of the foregoing, the power and authority to sign for, on behalf of
and in the name of the undersigned as a director of the Company, such Annual
Report and any amendments thereto filed with the Securities and Exchange
Commission and any instrument or document filed as part of, an exhibit to, or in
connection with said Annual Report or amendments thereto; and the undersigned
does hereby ratify and confirm as his own act and deed all that said
attorneys-in-fact and agents shall do or cause to be done by virtue hereof.

         IN WITNESS WHEREOF, the undersigned has subscribed these presents,
effective as of the 21st day of February, 1997.


                                                       /s/ Blake Eagle
                                                       -------------------------
                                                       Blake Eagle
<PAGE>   5
                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

         THAT I, Dr. Karl-Ludwig Hermann, a director of Cornerstone Properties
Inc. (the "Company"), do hereby constitute and appoint John S. Moody and Thomas
P. Loftus, and each of them, my true and lawful attorneys-in-fact and agents, to
do any and all acts and things and to execute any and all instruments which said
attorney and agent may deem necessary or advisable to enable the Company to
comply with the Securities Exchange Act of 1934, as amended, and any rules,
regulations and requirements of the Securities and Exchange Commission in
respect thereof, in connection with the filing under the said Securities
Exchange Act of the Company's Annual Report on Form 10-K for the fiscal year
ended December 31, 1996 (the "Annual Report"), including specifically, but
without limiting the generality of the foregoing, the power and authority to
sign for, on behalf of and in the name of the undersigned as a director of the
Company, such Annual Report and any amendments thereto filed with the Securities
and Exchange Commission and any instrument or document filed as part of, an
exhibit to, or in connection with said Annual Report or amendments thereto; and
the undersigned does hereby ratify and confirm as his own act and deed all that
said attorneys-in-fact and agents shall do or cause to be done by virtue hereof.

         IN WITNESS WHEREOF, the undersigned has subscribed these presents,
effective as of the 21st day of February, 1997.


                                                     /s/ Karl-Ludwig Hermann
                                                     -------------------------
                                                     Karl-Ludwig Hermann
<PAGE>   6
                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

         THAT I, Hans C. Mautner, a director of Cornerstone Properties Inc. (the
"Company"), do hereby constitute and appoint John S. Moody and Thomas P. Loftus,
and each of them, my true and lawful attorneys-in-fact and agents, to do any and
all acts and things and to execute any and all instruments which said attorney
and agent may deem necessary or advisable to enable the Company to comply with
the Securities Exchange Act of 1934, as amended, and any rules, regulations and
requirements of the Securities and Exchange Commission in respect thereof, in
connection with the filing under the said Securities Exchange Act of the
Company's Annual Report on Form 10-K for the fiscal year ended December 31, 1996
(the "Annual Report"), including specifically, but without limiting the
generality of the foregoing, the power and authority to sign for, on behalf of
and in the name of the undersigned as a director of the Company, such Annual
Report and any amendments thereto filed with the Securities and Exchange
Commission and any instrument or document filed as part of, an exhibit to, or in
connection with said Annual Report or amendments thereto; and the undersigned
does hereby ratify and confirm as his own act and deed all that said
attorneys-in-fact and agents shall do or cause to be done by virtue hereof.

         IN WITNESS WHEREOF, the undersigned has subscribed these presents,
effective as of the 21st day of February, 1997.


                                                    /s/ Hans C. Mautner
                                                    -------------------------
                                                    Hans C. Mautner
<PAGE>   7
                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

         THAT I, Gerald Rauenhorst, a director of Cornerstone Properties Inc.
(the "Company"), do hereby constitute and appoint John S. Moody and Thomas P.
Loftus, and each of them, my true and lawful attorneys-in-fact and agents, to do
any and all acts and things and to execute any and all instruments which said
attorney and agent may deem necessary or advisable to enable the Company to
comply with the Securities Exchange Act of 1934, as amended, and any rules,
regulations and requirements of the Securities and Exchange Commission in
respect thereof, in connection with the filing under the said Securities
Exchange Act of the Company's Annual Report on Form 10-K for the fiscal year
ended December 31, 1996 (the "Annual Report"), including specifically, but
without limiting the generality of the foregoing, the power and authority to
sign for, on behalf of and in the name of the undersigned as a director of the
Company, such Annual Report and any amendments thereto filed with the Securities
and Exchange Commission and any instrument or document filed as part of, an
exhibit to, or in connection with said Annual Report or amendments thereto; and
the undersigned does hereby ratify and confirm as his own act and deed all that
said attorneys-in-fact and agents shall do or cause to be done by virtue hereof.

         IN WITNESS WHEREOF, the undersigned has subscribed these presents,
effective as of the 21st day of February, 1997.


                                                    /s/ Gerald Rauenhorst
                                                    -------------------------
                                                    Gerald Rauenhorst
<PAGE>   8
                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

         THAT I, Berthold T. Wetteskind, a director of Cornerstone Properties
Inc. (the "Company"), do hereby constitute and appoint John S. Moody and Thomas
P. Loftus, and each of them, my true and lawful attorneys-in-fact and agents, to
do any and all acts and things and to execute any and all instruments which said
attorney and agent may deem necessary or advisable to enable the Company to
comply with the Securities Exchange Act of 1934, as amended, and any rules,
regulations and requirements of the Securities and Exchange Commission in
respect thereof, in connection with the filing under the said Securities
Exchange Act of the Company's Annual Report on Form 10-K for the fiscal year
ended December 31, 1996 (the "Annual Report"), including specifically, but
without limiting the generality of the foregoing, the power and authority to
sign for, on behalf of and in the name of the undersigned as a director of the
Company, such Annual Report and any amendments thereto filed with the Securities
and Exchange Commission and any instrument or document filed as part of, an
exhibit to, or in connection with said Annual Report or amendments thereto; and
the undersigned does hereby ratify and confirm as his own act and deed all that
said attorneys-in-fact and agents shall do or cause to be done by virtue hereof.

         IN WITNESS WHEREOF, the undersigned has subscribed these presents,
effective as of the 21st day of February, 1997.


                                                /s/ Berthold T. Wetteskind
                                                --------------------------------
                                                Berthold T. Wetteskind