Do not try the parallels in that way: I know that way all along. I have measured that bottomless night, and all the light and all the joy of my life went out there.

Published in: Samu Benkő (ed.), Bólyai-levelek, Kriterion, 1975, p. 123 | As quoted in: O'Connor, John J.; Robertson, Edmund F., "Farkas Bolyai", MacTutor History of Mathematics archive, University of St Andrews. | Having himself spent a lifetime unsuccessfully trying to prove Euclid's fifth postulate, Farkas discouraged his son János from any further attempt.