Quem Deus vult perdere, &c

Prescot, in his *History of the Conquest of Peru* (vol. ii., p. 404., 8vo. ed.), says, while remarking on the conduct of Gonzalo Pisaro, that it may be accounted for by "the insanity," as the Roman, or rather Grecian proverb calls it, "with which the gods afflict men when they design to ruin them." He quotes the Greek proverb from a fragment of Euripides, in his note:— "Οταν δε Δαιμων ανδρι παρσυνη κακα Τον νουν εβλαψε πρωτον." I wish to know whether the Roman proverb, *Quem vult perdere Deus prius dementat*, is merely a translation of this, or whether it is to be found in a Latin author? If t…