Spang writes about how the French aristocracy made what amounts to an annuity on the lives of a bundle of young French women -- you invested your money, then got a payout over time in proportion to how many of them stayed alive. The world's most bizarre financial product.

(I'm probably describing this badly bc I don't know a lot about these arcane financial instruments, and it's been years since I read the book.)

But basically, it opened my eyes to just how elaborate financial engineering gets. Indirectly, it's a nice counterpart to btc, where there is no magical 'yield' and you can understand exactly how the monetary elements works. But also unsettling a bit -- if people want these things and there's an appetite (as there has been, historically), then will they find some way to get them, e.g., all the fintech / defi stuff?