Who appeared with Jesus on the mountain when he prayed?

According to Luke 9:28-36 [28] And it came to pass about an eight days after these sayings, he took Peter and John and James, and went up into a mountain to pray. [29] And as he prayed, the fashion of his countenance was altered, and his raiment was white and glistering. [30] And, behold, there talked with him two men, which were Moses and Elias: [31] Who appeared in glory, and spake of his decease which he should accomplish at Jerusalem. [32] But Peter and they that were with him were heavy with sleep: and when they were awake, they saw his glory, and the two men that stood with him. [33] And it came to pass, as they departed from him, Peter said unto Jesus, Master, it is good for us to be here: and let us make three tabernacles; one for thee, and one for Moses, and one for Elias: not knowing what he said. [34] While he thus spake, there came a cloud, and overshadowed them: and they feared as they entered into the cloud. [35] And there came a voice out of the cloud, saying, This is my beloved Son: hear him. [36] And when the voice was past, Jesus was found alone. And they kept it close, and told no man in those days any of those things which they had seen.
See All..., Elias (the New Testament spelling of Elijah) and Moses met with Jesus on the mount. We even know what they talked about: "And, behold, there talked with him two men, which were Moses and Elias: Who appeared in glory, and spake of his decease which he should accomplish at Jerusalem" (Luke 9:30-31 [30] And, behold, there talked with him two men, which were Moses and Elias: [31] Who appeared in glory, and spake of his decease which he should accomplish at Jerusalem.
See All...). They spoke of the upcoming crucifixion ("decease") of Jesus Christ.

Let me mention one interesting thing about the meeting on the Mount of Transfiguration. Jesus went up and took three of His disciples: Peter, James, and John. That makes four people. Then, they were met by Elijah and Moses. That makes a total of six. Finally, the Father comes in a cloud and says, "This is my beloved Son: hear him" (Luke 9:35And there came a voice out of the cloud, saying, This is my beloved Son: hear him.
See All...). That makes seven on the mount. Seven in the Bible is the  number of perfection.