Harry Bates' "A Matter of Size" (novella, adventure): Splitting a man into multiple himselves & reassembling him back!
What happens to the individual experiences of the 9 tiny men at the time of reassembly? We aren't told about it; though we're told selective experiences, including those of the man-that-was before splitting, can be wiped out.
I don't know if this is the original, but it probably would be among the early stories, where someone is reduced to tiny size & has to undergo adventures in a world that to him would be a giants' world.
Story summary.Dr Arthur Allison, an "ethnologist", gets a visit & an offer by an alien: for 4 months, be alien's guest without being told why; or be forced to do it anyway! He "volunteers".
This is a crazy adventure on alien's world, his escape back to earth in a stolen spacecraft, chase after arriving & eventually getting caught - & being enlightened.
Fact sheet.First published: Astounding, April 1934.
Related: Works of Harry Bates.