An Historical Summary of Angelic Hierarchies from Part VII: The “Seven” Thrones in In Operibus Sigillo Dei Aemeth by David Richard Jones.
“In this way, Thrones became described as various types of fiery wheels in relation to their function in the chariot of God, as in Ezekiel 1: 15–20:
Now as I beheld the living creates, behold one wheel upon the earth by the living creatures, with his four faces. The appearance of the wheels and their work was like unto the color of a beryl: and they four had one likeness: and their appearance and their work was as it were a wheel in the middle of a wheel. When they went, they went upon their four sides: and they turned not when they went. As for their rings, they were so high that they were dreadful; and their rings were full of eyes round about them four. And when the living creatures went, the wheels went by them: and when the living creatures were lifted up from the earth, the wheels were lifted up. Withersoever the spirit was to go, they went, thither was their spirit to go; and the wheels of the living creature was in the wheels. When those went, these went; and when those stood, these stood; and when those were lifted up from the earth, the wheels were lifted up over against them: for the spirit of the living creature was in the wheels.” [via]