The Apologia and Florida of Apuleius of Madaura
Chapter 27
divination is preceded by sacrifice just as in Benvenuto Cellini (loc. cit.) the sorcerer first burns incense. The head is touched as being the source from which the oracle is to proceed (_arx et regia_, chap. 50). The clean robe is necessary, to ritual purity and is mentioned more than once in the magic papyri.