I was just reading Lord Kelvin's "The Sorting Demon Of Maxwell" where I found this quote concerning what Maxwell's Demon can do:
(He) can direct the energy of the moving molecules of a basin of water to throw the water up to a height and leave it there proportionately cooled (1 deg. Fahrenheit for 772 ft. of ascent)
Given this was written 135 years ago, I was wondering how in the world Lord Kelvin could possibly have calculated the kinetic energy of individual water molecules at different temperatures. Surely sophisticated statistical-mechanical theories of liquids weren't developed by 1878. What back-of-the-envelope calculation could he possibly have done?