I just tried to use Google to find a specific medieval spell used for summoning a flying horse. I know there is one, but can’t remember where it’s from or where to find it. You need a sceptre and a red bridle and what else? I don’t know. I didn’t write all of it down when I heard it used as an example in a conference paper.
It would be a dream come true if all medieval manuscripts were digitized and searchable across translations in a single database. Then I could find out the rest of the spell.
For the record, this “article” about medieval magic is one of the most untrue things I’ve read: Medieval Wicca & Sorcery.