I don't think this is exactly what you are asking, but I find analog computers[1] (specifically mechanical computers) fascinating, especially differential analy

I don't think this is exactly what you are asking, but I find analog computers[1] (specifically mechanical computers) fascinating, especially differential analyzers[2]. I knew of their existence but never really thought about them until reading some books related to Claude Shannon. It's still mind-boggling to me how they work. 1. https://en.wikipedia.org/wiki/Analog_computer https://en.wikipedia.org/wiki/Analog_computer 2. https://en.wikipedia.org/wiki/Differential_analyser https://en.wikipedia.org/wiki/Differential_analyser