Florian Hardwig pointed me to Haslam who calls this “tapered centring”. (German: Spitzkolumne) Thanks!
Is there a term in English for this kind of setting often seen in historical books? Centered setting with decreasing line lengths to make a roughly triangular shape.
See attached example of a Dutch book from the middle of the 18th century; I know the Hipnerotomachia Poliphili has beautiful ones too.
