I saw the video and i got so excited, that i had to know everything about this amazing mechanical calculator. People, i present to you, Curta, world's first portable calculator! And it is completely mechanical! This truly ingenious mechanism is designed to perform math functions like addition, subtraction, multiplication and division, and needs absolutely no external power supply!
The history of this gadget is even more amazing than its functionality. The device was designed by one man in a prison camp, working with paper and pencil!