For a closer look at how magic functions in the Decameron, we can examine three spells from various novellas and see how they resemble and share characteristics with other medieval spells. The first is a spell to exorcise a werewolf, the second for a woman to win back her lover, and the third an initiation procedure into a magical society. All of them incorporate real devices of magic: repetition, symbolism, pattern, rhyme, contiguity and so on, but Boccaccio purposefully contorts them into a humorous, satirical commentary on notions of magic in his day.
This pokes fun at several beliefs at once: imaginary creatures (the werewolf), the protection of prayer (Gianni says several and makes the sign of cross over the bed) and incantations meant to exorcise evil beings. The 'fine and godly prayer' begins with Tessa saying:
"Fantasima, fantasima che di notte vai, a coda ritta ci venisti, a coda ritta te n'andrai: va nell'orto, a piè del pesco grosso troverai unto bisunto e cento cacherelle della gallina mia: pon bocca al fiasco e vatti via, e non far mal né a me né a Gianni mio."
("Werewolf, werewolf, black as any crow, you came here with your tail erect, keep it up and go; go into the garden, and look beneath the peach, and there you'll find roast capons, and a score of eggs with each; raise the flask up to your lips, and take a swig of wine; then get you gone and hurt me not, nor even Gianni mine.")
While mainly a message to Federigo, the repetition, spitting, and lyric rhyming are genuine parts of spells. Repeating the entire spell, and the words 'werewolf, werewolf', enhances its power and chances of being effective. Spitting is common in exorcism rituals as an emphatic gesture to leave your mark on the spell and works by the Law of Contiguity which states that any two objects ever in contact with one another are symbolically equivalent in magic. Thus, his spit having been a part of him, gives it the force of his whole person in the exorcism. The spell is comical not only in its sexual metaphors but also because here he is backing his wife's relations with her lover. The final line, where Monna Tessa commands the werewolf to leave, exhibits the aspect of control in magic. An old distinction between religion and magic is that the former supplicates, while the latter makes demands.
This spell is more sophisticated than the first. The scholar gets his revenge on Elena and also teaches her how to obtain love in a sense larger than just the magical one. By the end of the tortuous process, the victim of the magic has been the widow, not her lover, and she has learned to think twice before playing tricks on others.
The spell requires that she be very brave and that she carry it out alone in a deserted place. She must:
By midnight on the following night her lover will have returned.
This ritual uses several magical techniques. The repetition of seven is a common magical motif. The number seven moves the moon, the seventh planet, which is associated with the goddess Diana who gave birth to the witch Aradia. (Noteworthy too is the fact that this tale is the seventh of the day.) The moon in the waning phase is also a reversal of magic; all spells should be performed under a waxing moon because it represents growing rather than diminishing power. The waning moon would signify weakness. Holding an image of the lover works by similarity, but if it contained something actually belonging to him such as a hair, a nail clipping or piece of clothing, it would function contiguously as well. The insistence on solitude in a deserted place is common to rituals because fear makes hallucination more likely and would traditionally enhance the power of the experience. This, however, is not fulfilled as Rinieri is spying on her from the bushes.
The high tower she must ascend is, of course, necessary for the scholar's plan of toasting her later under the sun, but the direction she faces on the tower is significant. He has her face north, but traditionally, when performing magic, one always faces east, in the direction of the rising sun. Her position would be a form of magical "sacrilege." The formula she repeats here could provide the main source of power for her love spell; however, the parchment Elena holds contains only "some nonsense concocted by [Rinieri] to serve as a formula."
In this novella, a true role reversal takes place. Master Simone, a physician recently arrived from Bologna, ought to be intelligent and discerning, above the realm of magic. But instead, the two painters Bruno and Buffalmacco play the physicians and concoct a scheme to gratify Master Simone's eagerness to participate in a secret, magical society. In "going the course," which is the climax of all his previous comical actions, Boccaccio has the doctor carry out procedures of actual societies, but changes them slightly in a very effective satirical twist.
The fantastic stories that Bruno and Buffalmacco weave about their society begin as completely outrageous, but eventually, at the master's prodding, they devise a plan to convey him to the meeting where he will be made a Knight of Bath. These are the steps he must follow:
This procedure makes it appear as though he were preparing for his induction into a diabolical society. Many magical societies required special costumes for their ceremonies. The freemasons used aprons, for instance, and witches danced without any clothes. Here, a robe is the traditional garb of a wizard or magus figure. The subsequent sullying of the rich robe is a further condemnation by the author of this type of activity. The necessity of bravery in the face of such an ordeal is also common to rituals. They are designed to scare the initiate, sometimes even role-playing his death so that he may be reborn in a new form, or into the new group.