Pliny the Elder [1st century CE] (Natural History, Book 10, 70): ...I judge [the pegasus] to be fabulous; and for my own part I think the same about the tragopan attested by a number of people, a bird larger than an eagle, having curved horns on the temples, in color a rusty red, except that its head is purple-red. - [Rackham translation]

Gaius Julius Solinus [3rd century CE] (De mirabilibus mundi / Polyhistor, Chapter 30.29): The tragopan is another bird, larger than an eagle. Its head is armed, and carries ram-like horns. - [Arwen Apps translation, 2011]

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Birds 5.114): Trogopales is a bird, as Solinus says, that is in Ethiopia. It is larger than the eagle. It has horns like a ram's; it prefers an armed head against all the birds opposed to it, driving them away with the harshness of its horns. This bird is of a rusty color. It has a head like that of a phoenix, except that it prefers an armed head, as we have said. - [Badke translation/paraphrase]