Macrobius, Saturnalia 5.1:
“The nature of orators is not, however, simple and unified: this one may flow and abound, but another might affect to speak briefly and concisely. One who is slight, dry, and sober loves a certain frugality of speech, but another luxuriates in rich, florid, and splendid speech. In this great difference among them all, Vergil alone is found to have conflated eloquence from every type. Avienus responded, ‘I would like if you could teach these diverse modes with the examples of individuals.’ Eusebius then said, ‘There are four modes of speech: the copious, in which Cicero is the master; the brief, in which Sallustius reigns supreme; the dry, which is ascribed to Fronto; and the thick and florid, in which Pliny the Younger once gloried, but in which our Symmachus yields to none of the ancients. But you will find these four types together in Vergil alone.”
Oratorum autem non simplex nec una natura est: sed hic fluit et redundat, contra ille breviter et circumcise dicere adfectat: tenuis quidam et siccus et sobrius amat quandam dicendi frugalitatem, aliud pingui et luculenta et florida oratione lascivit. In qua tanta omnium dissimilitudine unus omnino Virgilius invenitur qui eloquentiam ex omni genere conflaverit. Respondit Avienus: Apertius vellem me has diversitates sub personarum exemplis doceres. Quattuor sunt, inquit Eusebius, genera dicendi: copiosum, in quo Cicero dominatur: breve, in quo Salustius regnat: siccum, quod Frontoni ascribitur: pingue et floridum in quo Plinius Secundus quondam et nunc nullo veterum minor noster Symmachus luxuriatur. Sed apud unum Maronem haec quattuor genera repperies.