Compound interest

[…] tens of thousands of other foot passengers have been slipping and sliding since the day broke (if this day ever broke), adding new deposits to the crust upon crust of mud, sticking at those points tenaciously to the pavement, and accumulating at compound interest.

Arithmetic books published during the fifteenth and first half of the sixteenth centuries have little to say about interest although the practice of calculating compound interest was old at that time.