Fulgens Corona §16

¹⁶ Wherefore, right from ancient Church times, this tenet of doctrine both among pastors and in the minds and hearts of the people became daily more illustrious and more widespread. The writings of the Fathers bear witness to it; the Councils and the acts of the Roman Pontiffs declare it; and, finally, the ancient liturgies, in whose oldest sacred books this feast is mentioned as traditional, testify to it.