Stranger, dreams verily are baffling and unclear of meaning, and in no wise do they find fulfillment in all things for men. For two are the gates of shadowy dreams, and one is fashioned of horn and one of ivory. Those dreams that pass through the gate of sawn ivory deceive men, bringing words that find no fulfillment. But those that come forth through the gate of polished horn bring true issues to pass, when any mortal sees them. But in my case it was not from thence, methinks, that my strange dream came.
—Homer, The Odyssey, p. -1