Archimedes' principle
A Cartesian diver or Cartesian devil is a classic science experiment which demonstrates the principle of buoyancy (Archimedes' principle) and the ideal gas law. The first written description of this device is provided by Raffaello Magiotti, in his book (Very firm resistance of water to compression) published in 1648. It is named after René Descartes as the toy it is said to have been invented by him.