Water integrator

The Water Integrator was an early analog computer built in the Soviet Union in 1936. It functioned by careful manipulation of water through a room full of interconnected pipes and pumps. The level of water in various valves (with precision to fractions of a millimeter) represented stored numbers, and the rate of flow between them represented mathematical operations. Amazingly this machine was capable of solving non-homogeneous differential equations.

See also History of computers