On this day in 1504, Leonardo da Vinci demonstrates the first practical steam engine to his patron.

The inventor envisions the new engine as a power source for a number of other, previously unworkable inventions in his notebooks. His original engine, however, proves too inefficient to make these devices (which include versions of the tank, the submarine and the airplane) practical.

DaVinci wills his notebooks to the Vatican. However, by the tie he dies in 1519, copies of most of them have been secretly prepared by an assistant in exchange for large bribes. Their contents, which include a full description of da Vinci's engine, will inspire a wave of experimentation. Improved versions of the engine are put to work in such applications as pumping water from flooded mines.