For the math geeks out there:

Dante's Paradise, canto XXXIII, lines 133–135, contain the verse:

As the geometer his mind applies To square the circle, nor for all his wit Finds the right formula, howe'er he tries

Qual è ’l geométra che tutto s’affige per misurar lo cerchio, e non ritrova, pensando, quel principio ond’elli indige,