A man on acid.
What he sees:
The sudden appearance of a mountain. Perhaps like this one:
He spends days climbing the mountain. It is a long and beautiful journey. At the top of the mountain he finds God. He talks to God briefly, then jumps off the mountain.
What his friends see:
The man gets on the roof of his house. There he finds a flying disc, which he talks to for four hours. He then jumps off the roof of his house and breaks both legs.