Before we had the pocket calculators, computers were calculating a ton of things. Computers, as in: women who actually performed manual calculations like crazy. Damn, those women must have been hot.
Now, for about 3 decades the Curta Calculator was being used by engineers and scientist from the Western World. Each such calculator costed about $125, a lot for a regular human, but it was invaluable as it could perform additions, subtractions, division and multiplying all sorts of numbers.
The Curta Calculator is a mechanical calculator able to calculate even 46565*57588 for example. Using it was not easy, but it was and is an incredible engineering feat as the calculations it was doing were performed by gears, and some nuts and bolts moving around like crazy.
The Curta Calculator:
(image source: Wikipedia)