Witchcraft, Magic, and Alchemy by Grillot de Givry has got to be the weirdest book I have ever cracked. The publisher's product description is somewhat misleading:
From raising the dead to foretelling the future, this historical tour of the occult offers a captivating exploration of sorcery and ceremonial magic. Prepared by a noted French historian, it ventures into virtually all of the classical arts, with 375 rare black-and-white illustrations derived from paintings, illuminated manuscripts, sculpture, and architecture.
The author doesn't actually approach the material with the objective eye of a historian; he writes about necromancy and love philters and suchlike as if he actually believes in all this stuff. I can't decide if he's brilliant or cuckoo.
It is also very easy, according to several Black-books, to become invisible by carrying the heart of a bat, a black hen, or a frog under the right arm. A more elegant method is to wear the Ring of Gyges on your finger; you can then become visible or invisible at will simply by turning the stone inward or outward. This ring must be made of fixed mercury; it must be set with a little stone to be found in a lapwing’s nest, and round the stone must be engraved the words, “Jésus passant ✠ par le milieu d’eux ✠ s’en allait.” You must put the ring on your finger, and if you look at yourself in a mirror and cannot see the ring it is a sure sign that it has been successfully manufactured.How nutty is that? There's plenty more where this came from, but I left the book at Seanan's when I was moving out of Galway and forgot about it while I was in Tipperary, so further excerpts will have to wait.