Perpetual Motion
a motion which, once generated by mechanical means, should have the power of perpetuating itself. A machine which, according to the hopes of its inventors, after it has once set in motion, will keep in motion without drawing on any external source of energy. As early as 1775 the Académie des Sciences of Paris placed the problem in the same category with the duplication of the cube and the quadrature of the circle, and refused to receive schemes claiming to have overcome the difficulty-in reality, to have performed the impossible. The overbalancing wheel was a favorite contrivance with the seekers after a perpetual motion. It appears as early as the 13th century.