"At that time also, mischief not unlike the above appeared at Ravenna. A certain man named Vilgard occupied himself with more eagerness than constancy in literary studies, for it was always the Italian habit to pursue these to the neglect of the other arts. Then one night when, puffed up with pride in the knowledge of his art, he had begun to reveal itimself to be more stupid than wise, demons in the likeness of the poets Vergil, Horace, and Juvenal appeared to him, pretending thanks for the loving study which he devoted to the contents of their books and for serving as their happy herald to posterity. They promised him, moreover, that he would soon share their renown. Corrupted by these devilish deceptions, he began pompously to teach many things contrary to holy faith and made the assertion that the words of the poets deserved belief in all instances. But he was at last discovered to be a heretic and was condemned by Peter, archbishop of that city."Many others holding this noxious doctrine were discovered throughout Italy, and they too died by sword and pyre. Indeed, at this same period some went forth from the island of Sardinia--which usually teems with this sort of folk--to infect the people of Spain, but they were exterminated by the Catholics. This accords with the prophecy of the apostle John, in which he said that Satan would be released when a thousand years has passed. Of this we shall treat more fully in a third book"
- Vergilian Heresy: A Cautionary Tale
- Medieval Sourcebook: Ralph the Bald (ca.1025):Early Appearances of Heresy, c. 970
- Heretics and Scholars in the High Middle Ages, 1000-1200 by Heinrich Fichtenau (2000), see especially pp.13-15.
- Christianity: A Global History by David Chidester (2001), see especially pp. 258-259.
- Master Virgil: the author of the Æneid as he seemed in the middle ages; a series of studies by Joseph Salathiel Tunison (1886), see especially pp. 53-55.