Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
The age at which the orator should begin to plead will of course depend on the development of his strength. I shall not specify it further, since it is clear that Demosthenes pleaded against his guardians while he was still a mere boy, Calvus, Caesar and Pollio [*]( Demosthenes was 18, Crassus 19, Caesar 21, Asinius Pollio and Calvus not much older. See Tac. Dial. 34. ) all undertook cases of the first importance before they were old enough to be qualified for the quaestorship, others are said to have pleaded while still wearing the garb of boyhood, and Augustus Caesar delivered a funeral oration over his grandmother from the public rostra when he was only twelve years old.
In my opinion we should aim