"Pasajeros un de país antiguo"

Translating as 'Travellers from an antique land', this is almost certainly a reference to Percy Bysshe Shelley's 1818 sonnet Ozymandias:

 

Percy Bysshe Shelley
Public DomainPercy Bysshe Shelley - Credit: National Portrait Gallery

      Ozymandias

 

      I met a traveller from an antique land

      Who said: `Two vast and trunkless legs of stone

      Stand in the desert.

      Near them, on the sand,

      Half sunk, a shattered visage lies, whose frown,

      And wrinkled lip, and sneer of cold command,

      Tell that its sculptor well those passions read

      Which yet survive, stamped on these lifeless things,

      The hand that mocked them and the heart that fed.

      And on the pedestal these words appear --

      "My name is Ozymandias, king of kings:

      Look on my works, ye Mighty, and despair!"

      Nothing beside remains. Round the decay

      Of that colossal wreck, boundless and bare

      The lone and level sands stretch far away.'

 

The central theme of Shelley's poem is the impermanence of all great empires and civilizations, no matter how mighty. This theme is also central to Cormac McCarthy's novel.