Daydream, which is to thought as the nebula is to the star, borders on sleep, and is concerned with it as its frontier. An atmosphere inhabited by living transparencies: there’s a beginning of the unknown. But beyond it the Possible opens out, immense. Other beings, other facts, are there. No supernaturalism, only the occult continuation of infinite nature … Sleep is in contact with the Possible, which we also call the improbable. The world of the night is a world. Night, as night, is a universe … The dark things of the unknown world become neighbors of man, whether by true communication or by a visionary enlargement of the distances of the abyss … and the sleeper, not quite seeing, not quite unconscious, glimpses the strange animalities, weird vegetations, terrible or radiant pallors, ghosts, masks, figures, hydras, confusions, moonless moonlights, obscure unmakings of miracle, growths and vanishings within a murky depth, shapes floating in shadow, the whole mystery which we call Dreaming, and which is nothing other than the approach of an invisible reality. The dream is the aquarium of Night.
— VICTOR HUGO, LES TRAVAILLEURS DE LA MER
The Hugo citation comes from Ursula K. Le Guin’s 1971 novel The Lathe of Heaven—Le Guin uses it as a preface to the seventh chapter. It’s beautiful on its own; it also functions as a kind of poetic summary of The Lathe of Heaven.