New submitter GregLaden writes "The object known as the Galileo Thermometer is a vertical glass tube filled with a liquid in which are suspended a number of weighted glass balls. As the temperature of the liquid changes, so does the density. Since each glass ball is set to float at equilibrium in a sightly different density of the liquid, as the temperature increases, each glass ball sinks to the bottom. It turns out that this thermometer was actually invented by a team of instrument inventors that formed a scientific society who had the impressive motto 'Probando e Reprobando,' which in English means 'testing and retesting.' The Accademia del Cimento operated under the leadership of the Grand Duke Ferdinand II from 1657-1667 in Florence, Italy. According to Peter Loyson, who has written a corrective article for the Journal of Chemical Education, Galileo did invent a temperature measuring device called a thermoscope."