A medieval perpetual motion machine

A remarkable item from the sketchbook of Villard de Honnecourt—a medieval architect-engineer who flourished in the thirteenth century. A perpetual motion machine:

It reflects the general passionate interest of medieval men in natural sources of energy. They were power-conscious to the point of fantasy, always looking for sources of power beyond hydraulic, wind, and tidal energy.

Villard hoped that with mallets or bags filled with mercury assembled so as to swing freely “there will always be four on the downward side of the wheel and only three on the upward side; thus the mallet or bag will always fall over to the left as it reaches the top, ad infinitum.”

It is probably through the Islamic world that western Europe got involved in perpetual motion, but with the difference that Europe, given its interest in mechanization, would try to use perpetual motion as a practical source of energy.

Villard’s wide interest in an unlimited source of energy and in various types of machines makes him an archetypal engineer of the medieval industrial revolution (J. Gimpel, The Medieval Machine, 1976, 127–130).