  The sunspot groups have been observed since 1610 and their numbers have been
used for evaluating the amplitude of solar activity. Daniel M\"ogling recorded
his sunspot observations for more than 100 days in 1626 - 1629 and formed a
significant dataset of sunspot records before the Maunder Minimum. Here, we
have analysed his original manuscripts in the Universit\"ats- und
Landesbibliothek Darmstadt (ULBD) to review M\"ogling's personal profile and
observational instruments and derive number and positions of the sunspot
groups. In his manuscript, we have identified 134 days with an exact sunspot
group number and 3 days of additional descriptions. Our analyses have
completely revised their observational dates and group number, added 19 days of
hitherto overlooked observations, and removed 8 days of misinterpreted
observations. We have also revisited sunspot observations of Schickard and
Hortensius and revised their data. These results have been compared with the
contemporary observations. Moreover, we have derived the sunspot positions from
his sunspot drawings and located them at 2{\deg}-23{\deg} in the heliographic
latitude in both solar hemispheres. Contextualised with contemporary
observations, these results indicate their temporal migration to lower
heliographic latitudes and emphasise its location in the declining phase of
Solar Cycle -12 in the 1620s. His observations were probably conducted using a
pinhole and camera obscura, which made M\"ogling likely underestimate the
sunspot group number by >~ 33% - 52 %. This underestimation should be noted
upon their comparison with the modern datasets.
