Graphical quadratic formula solver from 1915 (nomogram)

If you like Nomograms or other mechanical mathematical curiosities, do check out @ChrisStaecker on YouTube. He does short, funny reviews/how-to videos for his collection of nomograms, measuring tools, mechanical and paper calculators. Unfortunately his channel also mixes his university lectures, so you have to check out his playlist [0]. Here's a nomogram for solving a quadratic equation. Check out the O-riginal video on YT! [1] [0] link [1] ▶ this video

For old calculating machines I want to recommend Prof. Chris Staecker's YouTube channel, his videos are enjoyable. Here is a play-list: ▶ this video Inspired me to buy a Comptometer: link If all you need to do is add, Comptometers are the fastest machines so far invented. They are fast because you can enter entire numbers at once (as a "chord" with multiple fingers pressing multiple digits at once). No need to hit "+" key or pull a lever between numbers, each button press is an immediate addition. I'm thinking of making an electronic version- it would have the same Comptometer key layout, but have more operations (for example, hold multiply "shift" key down while entering number for a multiply).