Sleep takes off the costume of circumstance, arms us with terrible freedom, so that every will rushes to deed. A skillful man reads his dreams for his self-knowledge; yet not the details, but the quality. What part does he play in them - a cheerful, manly part, or a poor, drivelling part? However monstrous and grotesque their apparitions, they have a substantial truth.

The Complete Works of Ralph Waldo Emerson: With a Biographical Introduction and Notes (ed. 1904)