After the First Council of Constantinople (381), the bishops sent out a letter about the doctrine they had affirmed. Among other things, it said:
According to this faith there is one Godhead, Power and Substance of the Father and of the Son and of the Holy Ghost; the dignity being equal, and the majesty being equal in three perfect hypostases, i.e. three perfect persons.
I'd like to know about that last word, "persons." I surmise that it's the Greek word prosopon. It's probably obvious why I think that. I don't need anyone to confirm to me that it's likely (or tell me it's not likely). Can anyone tell me (via direct evidence) what word is there in the original language of the letter?