Telling one's fortune by consulting the Æneid of Virgil. You take up the book, open it at random, and the passage you touch at random with your finger is the oracular response. Severus consulted the book, and read these words: “Forget not thou, O Roman, to rule the people with royal sway.” Gordianus, who reigned only a few days, hit upon this verse: “Fate only showed him on the earth, but suffered him not to tarry.” But, certainly, the most curious instance is that given by Dr. Wellwood respecting King Charles I. and Lord Falkland while they were both at Oxford. Falkland, to amuse the king, proposed to try this kind of augury, and the king hit upon bk. iv. ver. 881-893, the gist of which passage is that. “evil wars would break out, and the king lose his life.” Falkland, to laugh the matter off, said he would show his Majesty how ridiculously the “lot” would foretell the next fate, and he lighted on book xi. ver. 230-237, the lament of Evander for the untimely death of his son Pallas. King Charles, in 1643, mourned over his noble friend, who was shot through the body in the battle of Newbury.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894