The Roman poet Ovid states in his Metamorphoses that Morpheus is a son of Hypnos and reports that he had a thousand siblings, with Morpheus, Phobetor and Phantasos being merely the most prominent among them. Robert Burton, in his 1621 Anatomy of Melancholy, refers to Classical depictions of Morpheus, saying "Philostaratus paints [Morpheus] in a white and black coat, with a horn and ivory box full of dreams, of the same colours, to signify good and bad". Starting in the medieval period, the name Morpheus began to stand generally for the god of dreams or of sleep. In Carl Michael Bellman's Fredman's Epistle No. 72, "Glimmande nymf", Morpheus is invoked as the god of sleep.
- Burton, Robert. (2001), William H. Gass., eds., The Anatomy of Melancholy., New York, ISBN 9780940322660 .
- Griffin, A. H. F. (1997), A Commentary on Ovid, Metamorphoses XI, Hermathena, 162/163, Dublin, JSTOR 23041237.
- Kearns, E. (1996), "Morpheus", in S. Hornblower & A. Spawforth (eds.), Oxford Classical Dictionary (3rd rev. ed.), Oxford, ISBN 9780198661726 .
- Ovid, Metamorphoses, Brookes More. Boston. Cornhill Publishing Co. 1922. Online version at the Perseus Digital Library.