This motto on the world's most valuable postage stamp (British Guiana, 1856) was adapted from Horace, The Art of Poetry 11: (hanc veniam petimusque damusque vicissim), where Horace is both seeking and, in turn, granting poetic license:
‘But painters and poets
Have always shared the right to dare anything.’
I know it: I claim that licence, and grant it in turn.
(Τr. A. S. Kline)