From “A Treatise on Hygiene with special reference to the military service”, by William Alexander Hammond (Surgeon-General, U.S. Army.), published 1863, page 48.
“The haemodynamometer enables us to determine both the expiratory and inspiratory power, and is therefore more useful (figure 9). It consists of a bent tube of glass, attached to a scale graduated for both sides. An India-rubber tube is attached to one end of the glass tube, to which a suitable mouthpiece is affixed. Mercury is poured into the glass tube till the zero on both scales is reached. Upon expiring into the arrangement, the mercury is forced to rise in the opposite portion of the tube, and is correspondingly depressed in the portion to which the elastic tube is attached. When the act of inspiration is performed, the opposite movements of the mercury takes place. The same precautions are requisite as in using the cardiometer.
“The height to which the mercury be raised is greater by expiratory than by inspiratory efforts. A healthy man, five feet eight inches high, can raise the column of mercury about three inches by expiration, and about two inches by inspiration.”