late 19th century it was then adopted by two Americans, Matilda Joslyn Gage and Charles Leland, the latter of whom promoted a variant of it in his 1899 book, Aradia, or the Gospel of the Witches. The theory's most prominent advocate was the English Egyptologist Margaret Murray, who promoted it in a series of books – most notably 1921's The Witch-Cult in Western Europe and 1933's The God of the Witches. Almost all of Murray's peers regarded the witch-cult theory as incorrect and based on poor scholarship. However, Murray was invited to write the entry on "witchcraft" for the 1929 edition of the Encyclopædia Britannica, which was reprinted for decades and became so influential that, according to folklorist Jacqueline Simpson, Murray's ideas became "so entrenched in popular culture that they will probably never be uprooted." Simpson noted that the only contemporary member of the Folklore Society who took Murray's theory seriously was Gerald Gardner, who used it as the basis for Wicca. Murray's books were the sources of many well-known motifs which have often been incorporated into Wicca. The idea that covens should have 13 members was developed by Murray, based on a single witness statement from one of the witch trials, as was her assertion that covens met on the four cross-quarter days. Murray was very interested in ascribing naturalistic or religious ceremonial explanations to some of the more fantastic descriptions found in witch trial testimony. For example, many of the confessions included the idea that Satan was personally present at coven meetings. Murray interpreted this as a witch priest wearing horns and animal skins, and a pair of forked boots to represent his authority or rank. Most mainstream folklorists, on the other hand, have argued that the entire scenario was always fictitious and does not require a naturalistic explanation, but Gardner enthusiastically adopted many of Murray's explanations into his own tradition. The witch-cult theory was "the historical narrative around which Wicca built itself", with the early Wiccans claiming to be the survivors of this ancient pagan religion. The 'witch-cult' theory has since been disproven by further historical research, but it is still common for Wiccans to claim solidarity with witch trial victims. The notion that Wiccan traditions and rituals have survived from ancient times is contested by most recent researchers, who say that Wicca is a 20th-century creation which combines elements of freemasonry and 19th-century occultism. In his