Curta Mechanical Calculator

   I found this absolutely fascinating.  How the hell do you think of something like this???  I took a few mechanical design courses and I could barely figure out how to make a guage to determine out how much liquid was in a cylindrical container by using only mechanical means.
   Math geeks may recognize the iconic device pictured above. Before electronic calculators became available in the 70's, the Curta Calculator was considered to be the most efficient portable calculator available. The device boasts 605 intricate parts and it can perform addition, subtraction, multiplication, division, and even square roots without electricity. Despite its complexity, the Curta was so well constructed that it made a pleasing purring sound when the parts moved. It also happens to be one beautiful piece of machinery in general. However, the most interesting thing about the Curta may not be the design itself, but the story behind its creation.
   Curt Herzstark, the brilliant mind behind the calculator, completed the first prototypes in 1938, but he was imprisoned by the Nazis in the Buchenwald concentration camp shortly thereafter. His captors were aware of his work on the calculator, and ordered him to make a detailed drawing of the device so that the finished product could be delivered to Hitler as a gift after the end of the war. By liberation in 1945, Herzstark had successfully completed the drawing from memory, and his diligent work over the years undoubtedly helped keep him stay alive long enough to regain his freedom.