I find this very good review of Geosophia/Trve Grimoire/ St Cyprian ect. I like this part about the TG.
It is Stratton-Kent’s argument, and a pretty conclusive one at that, that the Grimoire Tradition is a survival and development of the eclectic blending of traditions represented in The Greek Magical Papyri. In the Geosophia he will go further back in history to investigate the nature and origin of the Papyri practices themselves, but for now this should be a sufficient discussion of the subject. To establish the link between the early modern grimoires, especially The True Grimoire, and the Magicial Papyri Stratton-Kent focuses on the topic of skrying, i.e. the Armadel method. This method shows up extensively within the Magical Papyri and in a form closely resembling that of The True Grimoire. Most simply the method is as follows: the magician or the magician and a seer that has been selected for the job sit with a skrying surface (water, ink, mirror, crystal, etc.) and an intermediary spirit is called into the surface (Scirlin, Uriel, Anubis, etc.). This intermediary then brings forth at the magicians request the other spirits whose presence is desired. The unification of the intermediary spirit and the Armadel method are, as Stratton-Kent explains, a central structure of The True Grimoire and likely also a missing or unstated key aspect of many of the other grimoires. In the Magical Papyri there is usually a bit more involved in this ritual. The intermediary spirit, once it appears, is first asked to set up a ritual scene. Often the request is for the spirit to set up a banquet with a set amount of chairs and so on. Then the spirit invites in a company of the gods, or spirits, to feast and celebrate after which the desired spirit can be spoken to for whatever purposes the magician has in mind. This method can similar be applied to the spirits of the dead as well. What makes this aspect so fascinating is, as Stratton-Kent points out, the extent to which it provides the performance of a full sacrifice and pagan ritual without the use of an actual temple, offering and so on. In other words, it places the role of pagan priest into the hands of the magician and allows a full large-scale religious ceremony to be performed in one’s own study. One can see the value of this, for example, for pagans living far from city centers with their own temple precincts and staff of priests or for those living in a context (political and social) which no longer facilitates or allows for the full practice of old collective pagan ceremonies. The common occult method of skrying, then, arises from a development, or decline, of standard pagan ceremony once the open practice of the various cults of the gods became for many reasons no longer as accessible.
The whole review is worth a read and the site is not too bad either.