I heard of/ read a grimoire called the Heptameron by Peter de Abano. This grimoire was mentioned/cited in the book Ceremonial Magic & The Power of Evocation by Joseph C. Lisiewski and, because of the simplicity of it's system in comparison to other grimoires like the Lesser Keys, I became interested in it.
The book utilizes a ritual circle, as do most grimoires, but this one is different in the sense that it changes depending on what day/hour you are working on. The spirit(s) you evoke also correspond to the day that you choose. The different spirits seem to relate to (the lower parts of) the planetary spheres. Just like in the Lesser Key, there is used a Hexagram (shown in the actual text) that is to be drawn on a "kid's skin parchment." The ritual also utilizes the obligatory white robe(or alb), the sword (but not fifty different swords), and the charcoal/incense (as well as holy water).
The book gives you a format to work with (blah blah in the name of blah, -Name of spirits- shall come forth blah blah) and some pretty simple instructions for being an old grimoire.
I was wondering if anyone has used this system and if it is effective. I myself am going to try soon (the dominican incense is in the mail). Hope those who didn't know about it will now get a chance to check it out.