Well, I have a much shorter work where I can trace the history, so I'll stick with only four.
1. Roverandom by J.R.R. Tolkien is a delightful children's tale of a toy dog who journeys to the moon and the sea.
2. The rhyme "Why the man in the moon came down too soon," also by Tolkien; from The Adventures of Tom Bombadil or The Tolkien Reader
3. A friend's comment:
The moon is a good hermit-hole for contemplating things that happen on the world below, and the earth atmosphere tends to be a bit thin. And if you want a third reason, I enjoy chatting with the man on the moon
4. My exhaustion after a week of orientation activities
Produced the poem "Hermit's Hidey-Tower." I'll only post the first verse to reserve rights if I ever want to publish it:
One night I found on a grassy mound
a shining silver stair
I stared in awe at what I saw
resting on the air
No rope or rail if I should fail
but stretching to the stars
stairs of light amidst the night
and a journey far