Ovid
The Metamorphoses of Ovid, Book X (Fable. 4)
Jupiter, charmed with the beauty of the youth Ganymede, transforms himself into an Eagle, for the purpose of carrying him off. He is taken up into Heaven, and is made the Cup-bearer of the Divinities.

Such a grove of trees had the bard attracted round him, and he sat in the midst of an assembly of wild beasts, and of a multitude of birds. When he had sufficiently tried the strings struck with his thumb, and perceived that the various tones, though they gave different sounds, still harmonize, in this song he raised his voice: “Begin, my parent Muse, my song from Jove, all things submit to the sway of Jove. By me, often before has the power of Jove been sung. In loftier strains have I sung of the Giants, and the victorious thunderbolts scattered over the Phlegræan plains.24 Now is there occasion for a softer lyre; and let us sing of youths beloved by the Gods above, and of girls surprised by unlawful flames, who, by their wanton desires, have been deserving of punishment.

“The king of the Gods above was once inflamed with a passion for Ganymede, and something was found that Jupiter preferred to be, rather than what he was. Yet into no bird does he vouchsafe to be transformed, but that which can carry his bolts.25 And no delay is there. Striking the air with his fictitious wings, he carries off the youth of Ilium; who even now mingles his cups for him, and, much against the will of Juno, serves nectar to Jove.”

Footnotes:

24. Phlegræan plains.]—Ver. 151. Some authors place the Phlegræan plains near Cumæ, in Italy, and say that in a spot near there, much impregnated with sulphur, Jupiter, aided by Hercules and the other Deities, conquered the Giants with his lightnings. Others say that their locality was in that part of Macedonia which was afterwards called Pallene; others again, in Thessaly, or Thrace.

25. Carry his bolts.]—Ver. 158. The eagle was feigned to be the attendant bird of Jove, among other reasons, because it was supposed to fly higher than any other bird, to be able to fix its gaze on the sun without being dazzled, and never to receive injury from lightning. It was also said to have been the armour-bearer of Jupiter in his wars against the Titans, and to have carried his thunderbolts.