Institutio Oratoria

It is for this reason that the famous piper Timotheus is said to have demanded from those who had previously been under another master a fee double the amount which he charged for those who came to him untaught. The mistake to which I am referring is, however, twofold. First they regard these inferior teachers as adequate for the time being and are content with their instruction because they have a stomach that will swallow anything:

this indifference, though blameworthy in itself, would yet be tolerable, if the teaching provided by these persons were merely less in quantity and not inferior in quality as well. Secondly, and this is a still commoner delusion, they think that those who are blest with greater gifts of speaking will not condescend to the more elementary details, and that consequently they sometimes disdain to give attention to such inferior subjects of study and sometimes are incapable of so doing.