"Chocolate Frogs have cards, inside them, you know, to collect -- famous witches and wizards. I've got about five hundred, but I haven't got Agrippa or Ptolemy."
-- Ron Weasley (PS6)
Heinrich Cornelius Agrippa von Nettesheim was scholar and author who wrote on many topics, including the occult. He appears on a Chocolate Frog trading card, which reads “celebrated wizard imprisoned by Muggles for his writing, because they thought his books were evil” (FW, PS6, CF). In September 1991, Ron tells Harry that ‘Agrippa’ is one of the Chocolate Frog cards he is missing from his collection.
In the Muggle version of history, Agrippa was a German soldier and physician, and an adept in alchemy, astrology, and magic. In his book De Occulta Philosophia (1531), Agrippa encouraged the study of magic, explaining the world in terms of cabalistic analyses of Hebrew letters and Pythagorean numerology; he believed that magic was the best means to know God and nature.
Legend has it that he "was always accompanied by a familiar in the shape of a large black dog." It was also said that "at the inns where he stayed, Agrippa paid his bills with money that appeared genuine enough at the time, but which afterward turned to worthless horn or shell, like the fairy money which turned to earth after sunset." (Source: Encyclopedia of Occultism and Parapsychology, 5th ed.)