There's a short poem that is often read at funerals in my home town in south Georgia, and at some point we had a conversation about where it came from. No one knew, and we speculated that it was some fragment of a poem by someone obscure. But it appears that it's an adaptation by Mark Twain/Samuel Clemens of a part of a poem by one Robert Richardson. It appears on the headstone of Twain's daughter.
The poem is:
Warm summer sun,
Shine kindly here,
Warm southern wind,
Blow softly here.
Green sod above,
Lie light, lie light.
Good night, dear heart,
Good night, good night.
Citation, which looks fairly authoritative, complete with a photo of the headstone. This other
citation, though looking even more academic, omits the Richardson source and says the poem is on Twain's wife's tomb, not his daughter's. I've written to the second site to suggest they check their source.
Update: got a nice note from citation #2 regretting the error and saying it had been corrected.