Evangelista Torricelli, a disciple of Galileo, demonstrates in 1643 in Florence that the atmosphere exerts pressure by filling a glass tube with mercury and inverting it over a basin: the mercury drops, creating a vacuum at the closed end — the first artificial vacuum produced in a laboratory — and stabilizes at a height proportional to atmospheric pressure. He publishes the results in a letter to Michelangelo Ricci (1644). The resulting instrument, the mercury barometer, is the basis of instrumental meteorology and the first experimental demonstration of the weight of air, refuting the Aristotelian axiom that "nature abhors a vacuum."