"Vannevar Bush, a professor at MIT [Massachusetts Institute of Technology] wanted to solve differential equations. Now, remember, in those days there weren’t computers like we have today. Everything had to be done by hand or with mechanical devices — adding machines, etc. A complicated differential equation, you perhaps couldn’t solve at all, or you could with a lot of manual labour with paper and pencil and calculations and adding and subtracting on these hand calculating machines." https://medium.com/motat/a-meccano-computer-motats-differential-analyser-bf7efe05232c