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.