“There are twin Gates of Sleep.
One, they say, is called the Gate of Horn
and it offers easy passage to all true shades.
The other glistens with ivory, radiant, flawless,
but through it the dead send false dreams up toward the sky.”
Source: Aeneid (29–19 BC), Book VI, Lines 893–896 (tr. Fagles); the gates of horn and ivory.
Original
Sunt geminae Somni portae, quarum altera fertur Cornea, qua veris facilis datur exitus umbris, Altera candenti perfecta nitens elephanto, Sed falsa ad caelum mittunt insomnia Manes.
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Virgil 138
Ancient Roman poet -70–-19 BCRelated quotes
Source: Translations, The Aeneid of Virgil (1866), Book VI, p. 228

"Although innumerable beings have been led to Nirvana no being has been led to Nirvana", §5, p. 85
Knots (1970)

"The Dunwich Horror " - Written Summer 1928; first published in Weird Tales, 13, No. 4, (April 1929)<!-- p. 481-508 -->
The Thing on the Doorstep (1937), first published in Weird Tales
Fiction
Context: Yog-Sothoth knows the gate. Yog-Sothoth is the gate. Yog-Sothoth is the key and guardian of the gate. Past, present, future, all are one in Yog-Sothoth. He knows where the Old Ones broke through of old, and where They shall break through again. He knows where They have trod earth's fields, and where They still tread them, and why no one can behold Them as They tread.

“Who will remember, passing through this Gate,
The unheroic Dead who fed the guns?”
"On Passing the New Menin Gate" (1927-1928)
Collected Poems (1949)
Context: Who will remember, passing through this Gate,
The unheroic Dead who fed the guns?
Who shall absolve the foulness of their fate, —
Those doomed, conscripted, unvictorious ones?
Crudely renewed, the Salient holds its own.
Paid are its dim defenders by this pomp;
Paid, with a pile of peace-complacent stone,
The armies who endured that sullen swamp.

“The Gate is Straight, Deep and Wide; Break On Through to the other side.”

“Truth is an arrow, and the gate is narrow that it passes through.”
Song lyrics, Slow Train Coming (1979), When He Returns