Let me explain an example: an Italian craftsman in the early Renaissance rediscovered Archimedes screw and guessed to use it as a pump to supply water to the top (a screw every reader saw grinder - where he delivers the meat to the knives). But this seems a little inventor. He immediately builds a device of the two tanks, the upper and lower, Archimedean screw and water wheels. According to his plan was to rotate the wheel bolt, and screw pump water to the upper tank. Perpetual motion! Alas, the upper tank emptied quickly and would not be filled. Inventor endlessly improving their device, ruined, it ends a life of poverty, not knowing that he, along with other such failures did much to justify the first law of thermodynamics.