Even so, it is often combined with the metric prefix milli to name one millitorr (mTorr), equal to 0.001 Torr.
The unit was named after Evangelista Torricelli, an Italian physicist and mathematician who discovered the principle of the barometer in 1644.
Torricelli attracted considerable attention when he demonstrated the first mercury barometer to the general public.
In honour of Torricelli, the torr was defined as a unit of pressure equal to one millimeter of mercury at 0 °C.
This yields a precise definition that is unambiguous and independent of measurements of the density of mercury or the acceleration due to gravity on Earth.
[4] Nevertheless, manometric units are routinely used in medicine and physiology, and they continue to be used in areas as diverse as weather reporting and scuba diving.