The Art Notorious
Another medieval magic text was the Art Notorious, or Art of Memory. It promised, among other things, to give the reader the power to commit to memory any text, no matter how long. This was done by imagining (or actually) walking through a vast cathedral or magical symbol, and at each stop associating the place with the words to be remembered. It also contained this tongue twister that was supposed to be a prayer/spell to give the reader eloquence:
Thezay lemach ossanlomach azabath azach azare gessemon relaame azathabelial biliarsonor tintingote amussiton sebamay halbuchyre gemaybe redayl hermayl textossepha pamphilos Cytrogoomon bapada lampdayochim yochyle tahencior yastamor Sadomegol gyeleiton zomagon Somasgei baltea achetom gegerametos halyphala semean utangelsemon barya therica getraman sechalmata balnat hariynos haylos halos genegat gemnegal saneyalaix samartaix camael satabmal simalena gaycyah salmancha sabanon salmalsay silimacroton zegasme bacherietas zemethim theameabal gezorabal craton henna glungh hariagil parimegos zamariel leozomach rex maleosia mission zebmay aliaox gemois sazayl neomagil Xe Xe Sepha caphamal azeton gezain holhanhihala semeanay gehosynon caryacta gemyazan zeamphalachin zegelaman hathanatos, semach  gerorabat syrnosyel, halaboem hebalor halebech ruos sabor ydelmasan falior sabor megiozgoz neyather pharamshe forantes saza mogh schampeton sadomthe nepotz minaba zanon suafnezenon inhancon maninas gereuran gethamayh passamoth theon beth sathamac hamolnera galsemariach nechomnan regnali phaga messyym demogempta teremegarz salmachaon alpibanon balon septzurz sapremo sapiazte baryon aria usyon sameszion sepha athmiti sobonan Armissiton tintingit telo ylon usyon, Amen.
What interests me about all of these magic books is that they actually would have worked. Trithemius's book did send undetectable messages, the Art of Memory did increase the ability to remember, and the spell for eloquence really would have been good practice for speaking.
What they have in common is that they were magic about the mind. Magic words can affect reality, but only by passing through a mind into a body and out into the world. The act of speaking "I do" creates a real and permanent change in the world if spoken during the proper ceremony, along with the rings of binding.
When people say that magic is only an illusion, or a trick, they're missing the point. Creating the illusion in people's minds is the magic.