Sources : Ibex
Pliny the Elder [1st century CE] (Natural History, Book 8, 79): ...the ibex — an animal of marvelous speed, although its head is burdened with enormous horns resembling the sheaths of swords, towards which it sways itself as though whirled with a sort of catapult, chiefly when on rocks and seeking to leap from one crag to another, and by means of the recoil leaps out more nimbly to the point to which it wants to get. - [Rackham translation]
Isidore of Seville [7th century CE] (Etymologies, Book 12, 1:16-17): And a wild goat is likewise ... an ibex, as if the word were avex, because they hold to the steep and lofty places as the birds [avis] do, and inhabit the heights, so that from these heights they are scarcely [vix] visible to human gaze. Whence also the southern part of the world calls the birds that inhabit the floods of the Nile ibexes [a confusion with the ibis]. These animals, as we have said, dwell in the highest crags, and if ever they espy danger from beasts or humans, they throw themselves down from the highest peaks on their horns and lift themselves up unharmed.- [Barney, Lewis, et. al. translation]
Aberdeen Bestiary [circa 1200 CE] (folio 11r-11v):There is an animal called the ibex, which has two horns of such strength that, if it were to fall from a high mountain to the lowest depths, its whole body would be supported by those two horns. The ibex represents those learned men who are accustomed to manage whatever problems they encounter, with the harmony of the two Testaments as if with a sound constitution; and, supported as by two horns, they sustain the good they do with the testimony of readings from the Old and New Testament.
Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Quadrupeds 4.50): The ibex are beasts, which, as the blessed Gregory says in the Morals, are small in body. They live in rocks and there they breed. They have horns with which, when they feel that danger is imminent, they throw themselves from the rocks, and land on their horns; and thus remain immune from all injury. - [Badke translation/paraphrase]