Said Rabbi Ishmael: Thus did Rabbi Nehunya ben Hakkanah say to me: Totrosi’ai the Lord God of Israel of Hosts sitteth within seven palaces, one within another. And at the entrance to each palace are eight door-keepers, four to the right of the lintel and four to the left of the lintel.
Nehunya ben Hakkanah Teaches Heavenly Ascent
Heikhalot Rabbati 17:1