" He also sent messengers to Pope Leo III., with the request to sanction the insertion of the clause in the Nicene Creed. The pope decided in favor of the doctrine of the double procession, but protested against the alteration of the creed, and caused the Nicene Creed, in its original Greek text and the Latin version, to be engraved on two tablets and suspended in the Basilica of St. Peter, as a perpetual testimony against the innovation. "

― Philip Schaff , History of the Christian Church, 5th, Thoroughly Revised Edition (Complete Vol.1-7) (With Active Table of Contents)