On June 11. 1644, Italian scientist Evangelista Torricelli wrote to his friend Michelangelo Ricci describing his new invention, a mercury barometer.

I have already called attention to certain philosophical experiments that are in progress … relating to vacuum, designed not just to make a vacuum but to make an instrument which will exhibit changes in the atmosphere, which is sometimes heavier and denser and at other times lighter and thinner. Many have argued that a vacuum does not exist, others claim it exists only with difficulty in spite of the repugnance of nature; I know of no one who claims it easily exists without any resistance from nature.
Evangelista Torricelli (1608 – 1647) – Biography – MacTutor History of Mathematics

Evangelista Torricelli (1608-1647)
From the Famous Italians series
Issued in 1958 by Italy
Designer: Giovanni Savini