In a trance the busy daytime mind steps aside, and images begin to rise on their own. A wide sheet, held at its four corners, comes down from above. The number four is one of the oldest signs the mind uses for something complete, whole on every side, like the four directions of the earth.
What comes down is not invented by the man praying. It descends into him from the deeper layer of the mind, offering something his narrow daylight self had shut out. The vision widens him, showing that what he had judged unclean belongs, after all, inside the whole.