Torricelli's experiment

[1] For much of human history, the pressure of gases like air was ignored, denied, or taken for granted, but as early as the 6th century BC, Greek philosopher Anaximenes of Miletus claimed that all things are made of air that is simply changed by varying levels of pressure.

In the 17th century, Evangelista Torricelli conducted experiments with mercury that allowed him to measure the presence of air.

The discovery helped bring Torricelli to the following conclusion: We live submerged at the bottom of an ocean of the element air, which by unquestioned experiments is known to have weight.This test was essentially the first documented pressure gauge.

In 1647 Valerianus Magnus published his Demonstratio ocularis, in which he claims to have proved the existence of the vacuum in the court of the king of Poland, Ladislaus IV, in Warsaw by means of an experiment identical to that carried out by Torricelli three years earlier.

Three months after Magnus, Blaise Pascal published his Expériences nouvelles touchant le vide, giving details of his first barometric experiments.