29-19 BCE — Virgil, Aeneis, Book VI, lines 124-127
Talibus orabat dictis, arasque tenebat, cum sic orsa loqui vates: "Sate sanguine divom, Tros Anchisiade, facilis descensus Averno; noctes atque dies patet atri ianua Ditis;"
Then thus replied the prophetess divine: "O goddess-born of great Anchises' line, The gates of **** are open night and day; Smooth the descent, and easy is the way: (loose translation by John Dryden, 1697)
Etymology
Literally "The descent to Avernus is easy." From Virgil's Aeneid, with reference to Avernus, a metonym for the underworld and to Lake Avernus in Italy, a volcanic crater lake reputed to emit deadly vapors.