An Historical Summary of Angelic Hierarchies from Part VII: The “Seven” Thrones in In Operibus Sigillo Dei Aemeth by David Richard Jones.

“This description is particularly appropriate to their placement on and derivation from the Circumference of the Sigillum, in that the Circumference itself is one great wheel and the names as drawn therefrom form both wheels about and within this larger wheel, as well as figures like unto lighting bolts.” [via]