Augustus De Morgan, A Budget of Paradoxes, 2nd edition, D. E. Smith ed., Open Court Publishing, Chicago, 1915, vol 2, p 360. (The first clause, more common in English as "Speech was given to man to disguise his thoughts", was apparently coined by Harel but ascribed by him to Tallyrand. See Bartlett's Familiar Quotations.)

When I worked at the Royal Aircraft Establishment I used to ask my superiors, from time to time, whether it would not perhaps be better if aeroplanes had feathers; but I seldom succeeded in extracting a rational or even a patient answer to this question.