William Beckford’s 1835 travel memoir Italy: With Sketches of Spain and Portugal contains a startling episode in the monastery El Escorial, near Madrid:

Forth stalked the prior, and drawing out from a remarkably large cabinet an equally capacious sliding shelf–(the source, I conjecture, of the potent odour I complained of)–displayed lying stretched out upon a quilted silken mattress, the most glorious specimen of plumage ever beheld in terrestrial regions–a feather from the wing of the Archangel Gabriel, full three feet long, and of a blushing hue more soft and delicate than that of the loveliest rose. I longed to ask at what precise moment this treasure beyond price had been dropped–whether from the air–on the open ground, or within the walls of the humble tenement at Nazareth; but I repressed all questions of an indiscreet tendency–the why and wherefore, the when and how, for what and to whom such a palpable manifestation of archangelic beauty and wingedness had been vouchsafed.

It should be noted that Beckford was something of an eccentric; his enormous country house had collapsed 10 years earlier, and perhaps his writings too were built on dreams. But the monks aren’t telling.