Before the miniaturization of transistors, computers had a much more visible system of counting: Things like gears, pivots, beads and levers were often used and they needed some sort of power source to function. Vladimir Lukyanov built something like this in 1936 but he used water to create a computer that solved partial differential equations. In images of the Lukyanov computer, you'll see a complex system of interconnected tubes filled with water. Adjusting taps and plugs altered the flow of water (and changed variables) while the end result was seen by measuring the level of water in certain tubes. It was also called a Water Integrator and was originally designed to solve the problem of cracking in concrete. It's now found in Moscow's Polytechnic Museum