One of the problems that engaged engineers in the years between the XVIII and the XIX centuries was that of finding a useful system to drive the axle of the piston of a steam engine with a rectilinear reciprocating motion. In 1784 James Watt, the inventor of the steam engine, conceived a mechanism, later widely used, that approximately solved the problem of the rectilinear motion. The exact solution to this problem was found by Peaucellier in 1864, when he created the mechanism reproduced in the photograph. It is made of seven hinged axles, known as the Peaucellier cell.