Evangelista Torricelli (1608-1647)

Torricelli was an Italian mathematician and physicist.
He discovered the principle of the barometer.
He put a long Mercury-filled glass tube, closed at one end, upside-down in a cup of mercury.
The air pressure on the surface of the mercury in the cup held the column of mercury in the tube at a height of 760 mm.
The weight of the column of mercury was equal to the pressure of the atmosphere.


Complete here