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

“It is in the Celestial Hierarchy that the Thrones become situated and defined with the structure of subsequent Christian metaphysics, and from this context that essentially all further elaborations are derived.

The Thrones and their celestial functions are given in chapters II, V–VII, and XI of the Celestial Hierarchy, wherein they are described as being symbolically represented by ‘some kind of fiery wheels above the heavens, or material thrones upon which the Supreme Deity may recline,’ and further as great wheels, covered with numerous eyes, marking the end of the uppermost choir or hierarchy of angels where the emanations from God begin to take on material form.” [via]