[pests]

Ah yes! That would totally line up. Guessing from his Surely You're Joking book.

Apologies to any if I butchered the story or experiment, been awhile.

[frabcus]

It's definitely in the excellent Feynman BBC series "Fun to imagine"

[pests]

I've never watched but I'll have to check it out! Must be a common story he tells haha.