Is this off the back of a video of a 1970s Open University style presenter showing the properties of isochromus curves - i loved watching it and realised that these are national treasures of programs - and also was quite stunned by the assumption one would have a round empty tobacco tin lying around to do the experiment with - times do chnage :-)
I suspect it is... It turned up in my YouTube suggestions yesterday. Here's a link: https://youtu.be/eBc827pwKf0
Feynman's Lost Lecture (ft. 3Blue1Brown) [video] https://news.ycombinator.com/item?id=17927217