Judy, from the CLV.
Mat 17:3 And lo! Moses and Elijah were seen by them, conferring with Him.
Vs. 7 and 8. And Jesus approached and, touching them, said, "Be roused, and fear not!" Now, lifting up their eyes, they perceived no one except Jesus Himself only.
vs 9. ...Jesus directs them, saying, "Now you may tell no one (of) the vision till the Son of Man(kind) may be roused from among the dead."
vs 10. ...'why then are the scribes saying that Elijah must be coming first?" vs.12 ...Yet I am saying to you that Elijah came already, and they didn't recognize him, but they do to him whatever they will. Thus the Son of Man is also about to be suffering by them." Then the disciples understand that He spoke to them concerning John the Baptist.
Peter, James and John go the mountain with Christ. He was transfigured in front of them. Moses and Elijah were SEEN by them. The voice from Heaven identifies Jesus. They fall to their knees, and when they dare again open their eyes, they see Christ alone. Jesus calls what they experienced a vision. He explains that the prophecy regarding Elijah WAS fulfilled, and the disciples understood that a man (John the Baptist) came with the spirit of Elijah.
A vision, and a type.
It wasn't the last vision and revelation of a type that Peter had, and it certainly wasn't the last time it happened to John either, as the recorder of The Revelation.