Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
For the writers of text-books do not forbid it because they regard it as illicit, but because they think it useless. Consequently if its utility be proved, we shall have to employ it for the very reason for which we are now forbidden to do so.