The Arabic author, Haly Abou Gefar, tells of a golden ball used by “the Magi, followers of Zoroaster,” in their incantations. It was incrusted with celestial symbols and set with a sapphire, and one of these magicians, after attaching it to a strip of bullhide, swung it around, reciting at the same time various spells and incantations.[271] Probably the magician, by fixing his gaze upon the brilliant revolving sphere, gradually fell into a hypnotic trance, during which visions appeared to him. These he could afterward interpret to those who had sought his aid to read the future, or obtain information regarding things that were happening far away. An important side-light on the beliefs of Western Europe, in the fifth century, regarding crystal-gazing, is afforded by one of the canons of the synod held about 450 A.D. by St. Patrick and the bishops Auxilius and Issernanus. Here it is decreed that any Christian who believes there is a Lamia (or witch) in the mirror is to be anathematized, and is not to be again received into the Church unless he shall have renounced this belief and shall have diligently performed the penance imposed upon him.[272] In this case, as in many others, the vision in the crystal or mirror did not represent some former or contemporaneous happening, but the figure of an evil spirit, who, either by signs or words, imparted to the scryer the information he was seeking. The power to see images of evil spirits on the surface of water was claimed by those called _hydromantii_ in the ninth century. This is attested in a work composed about 860 A.D. by Hincmar, Archbishop of Rheims, who characterizes the supposed appearances as “images or deceptions of the demons.” These diviners asserted that they received audible communications from the spirits, and they therefore evidently believed that the appearances were realities.[273] Although, as we have seen, many different materials were used for scrying, the preference was often given to polished spheres of beryl; in modern times, however, the rock-crystal is considered the best adapted for the purpose. In his introduction to “Crystal Gazing,” by N. W. Thomas,[274] Andrew Lang writes of what he terms hypnagogic illusions—images which appear when the eyes are closed and before sleep supervenes. When faces appeared to him in this way, they were always unfamiliar ones, with the single exception of having once seen his own face in profile. The same was almost invariably true of landscape and inanimate objects. These forms seemed to grow out of the bright points of light which frequently appear when the eyes are closed, and Lang suggests a similar origin for the visions of the “scryers”—namely, the development of the images from dark or light points in the glass. In regard to this, we have an interesting passage in the works of Ibn Kaldoun, a Persian writer, born in 1332, who gives the following very acute analysis of the phenomena accompanying crystal-gazing.[275]