Lilith's Cave - Jewish Tales of the Supernatural | Selected and Retold by Howard Schwartz
"If you want to discover demons, take sifted ashes and sprinkle them around your bed, and in the morning you will see something like the footprints of a cock. If you want to see them, take the after-birth of a black she-cat, the firstborn of a firstborn, roast it in fire and grind it to powder, and then put some in your eye and you will see them."
—The Talmud
Berachot 6a