The Binary Marble Adding Machine by Matthias Wandel is just extraordinary. It’s a simple 6-bit calculator that’s completely analog, meaning that the entire thing is made of wood and is activated by marbles! There are no actual computer parts to this calculator. You can think of it as a distant cousin of the abacus (but personally, the abacus is boring).

Matthias Wandel explains the machine much better than I ever could, so just watch the video below and be in awe of this magnificent invention.

You can buy one for $250.