Da Vinci's Mechanical Hammer Paper Model.

This is a paper model of da Vinci's mechanical hammer:

This is one of the simplest machines designed by Leonardo in order to improve the human performance. A lever connected to the hammer is moved by means of an eccentric cam. At each turn of the handle, the hammer gives a stroke. As a matter of fact, the real hammer is supposed to be powered by a water paddle-wheel.

Link - via Paper Forest