Sentence:  Over a temperature range from 25 to 200 * * f and at pressures up to 250 atm , an overload of 300 psi , applied for a period of one day , results in an uncertainty in the pressure of , at most , one <WSD>millimeter</WSD> of mercury . 
Meaning of the word marked with <WSD> tags:  a unit of pressure equal to 0.001316 atmosphere; named after Torricelli