The Curta mechanical calculator is an incredible feat of mechanical engineering. Developed in the 1940s, these devices are roughly the size and shape of a salt shaker. When a series of mechanical sliders and a carriage set correctly, it can makes calculations with the turn (or turns) of a handle. The results can then be reset using a lever, making for a very interesting piece of mechanical hardware.
Though it’s amazing what this device can do, its origin story is perhaps even more incredible. Its creator, Curt Herzstark, was taken to the Buchenwald concentration camp in 1943, where rumors spread that he was working on a new calculating machine. Strangely enough, development of this device was encouraged as something that could be presented to Adolf Hitler upon Germany’s predicted victory in World War II. As this prediction didn’t come to fruition, Herzstark was able to make working prototypes of this invention after the war, and then put them into production under his own name. This continued until they were phased out in the 1970s with the invention of the electronic calculator.