If you're reading Middle High German texts, there's occasionally the mention of peacock feathers in clothing - quite often it's a "peacock hat", but sometimes there's also a reference to other garments in a kind of peacock-y style.

Nobody really knows what this kind of fabric was (or if there's several variations)... but I have now actually stumbled across a real piece of extant fabric that includes peacock feathers!

It was found in a relic case in St. Rumbold Cathedral, Mechelen, Belgium. The fabric has been radiocarbon dated to the 13th century, and it is a red cut velvet (silk pile on linen ground weave); applied across it, in a kind of cross-hatch pattern, are peacock feathers and gold threads (gilt silver around a silk core). Unfortunately the text doesn't say how exactly they were attached - but I'm utterly thrilled anyways.

It has been published in an article aptly named "A Box Full of Surprises" (available on academia.edu).

This is... way cool!