The Iliad by Homer Book 14 Page 18

And Juno said, “Sleep, why do you take such notions as those into your head? Do you think Jove will be as anxious to help the Trojans, as he was about his own son? Come, I will marry you to one of the youngest of the Graces, and she shall be your own — Pasithea, whom you have always wanted to marry.”

Sleep was pleased when he heard this, and answered, “Then swear it to me by the dread waters of the river Styx; lay one hand on the bounteous earth, and the other on the sheen of the sea, so that all the gods who dwell down below with Saturn may be our witnesses, and see that you really do give me one of the youngest of the Graces — Pasithea, whom I have always wanted to marry.”

Juno did as he had said. She swore, and invoked all the gods of the nether