I was googling *back of the envelope* for a recent post and I came across these lecture notes by Victor Weisskopf from 1969.

I can no longer really follow this sort of thing—I really really wish this had been my textbook back when I was studying physics. If they’d taught us this stuff, I might’ve never left that field.

Anyway, here’s one of the more accessible bits, from page 8-11 of the document, where he derives that a mountain must be less than 30 km high to be supported by the rock at its base:

In the next section, Weisskopf derives the number of atoms in a liquid from its surface tension and latent heat of evaporation:

I’m really annoyed that physics wasn’t taught this way to me. That said, it’s a challenge to write a statistics book of this sort. I’m working on it; I have various examples that have this flavor.