The Lesser Key of Solomon
In medieval ceremonial magic, the term "sigil" was commonly used to refer to occult signs which represented various angels and demons which the witch might summon. The magical training books called grimoires often listed pages of such sigils. A particularly well-known list is in "The Lesser Key of Solomon", in which the sigils of the 72 princes of the hierarchy of hell are given for the magician's use. Such sigils were considered to be the equivalent of the true name of the spirit and thus granted the magician a measure of control over the beings.