How to identify Satan: look up his nose

For as I have conceived by some disciples of necromancy, the which have it in science for to make advocation of wicked spirits, and by some unto whom the fiend hath appeared in bodily likeness; that in what bodily likeness the fiend appeareth, evermore he hath but one nostril, and that is great and wide, and he will gladly cast it up that a man may see in thereat to his brain up in his head. The which brain is nought else but the fire of hell, for the fiend may have none other brain; and if he might make a man look in thereto, he wants no better. For at that looking, he should lose his wits for ever.
-- The Cloud of Unknowing, anon. 14th c. (via Julia Morton)