Ivory Gate of Dreams
(The). Dreams which delude pass through this gate, those which come true pass through the Gate of Horn. This fancy depends upon two puns: ivory in Greek is elephas, and the verb elephairo means “to cheat with empty hopes;” the Greek for horn is keras, and the verb karanoo means “to accomplish.”
Sunt geminæ somni portæ: quarum altera fertur Cornea, qua veris facilis datur exitus umbris; Altera candenti perfecta nitens elephanto; Sed falsa ad coelum mittunt insomnia manes.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894