Quintilian (3.7.28, tr. H. Butler) says, "Panegyrics have been composed on sleep and death." Here's a sonnet on sleep by Wordsworth:
A flock of sheep that leisurely pass by
One after one; the sound of rain, and bees
Murmuring; the fall of rivers, winds and seas,
Smooth fields, white sheets of water, and pure sky —
I've thought of all by turns, and still I lie
Sleepless; and soon the small birds' melodies
Must hear, first utter'd from my orchard trees,
And the first cuckoo's melancholy cry.
Even thus last night, and two nights more I lay,
And could not win thee, Sleep, by any stealth:
So do not let me wear to-night away.
Without thee what is all the morning's wealth?
Come, blessed barrier between day and day,
Dear mother of fresh thoughts and joyous health!
John G. Fitch, commentary on Seneca, Hercules Furens
Addresses and prayers to Sleep include Hom. Il. 14.233ff. (by Hera), Eur. Or. 211ff. (by Orestes), Soph. Phil. 827ff. (a choral ode), Hymn. Orph. 85, Ov. Met. 11.623ff. (by Iris), Stat. Silv. 5.4 (by the poet himself), Theb. 10.126ff. (by Iris), Val. Fl. 8.70ff. (by Medea), Sil. 10.343ff. (by Juno).
See also Michael Hendry's web pages on Sonnets to Morpheus