Charles Dickens. Posthumous notes of the Pickwick club (№ 292341)

An old joke - not bad, although plausible, a young Irish gentleman on the question of whether he knows how to play the violin, replied that nothing in this no doubt, but to say do not dare, because never tried. ... Gentlemen, it only proves the validity of the old rule: one never knows what he's capable of, until then, until you check on the case.