Two things that landed on a 21st of September
On 21 September 1937, Allen & Unwin printed 1,500 copies of The Hobbit. It sold out by December. The book started as a scrap in a margin: Tolkien was marking exam papers, found a blank page, and wrote “In a hole in the ground there lived a hobbit.” He did not know yet what a hobbit was.
Same date, forty years earlier. On 21 September 1897, The Sun in New York printed a 416-word answer to an eight-year-old who had asked whether Santa Claus was real. It ran unsigned, as staff editorials did. The paper never put a name to it, and did not name its writer, Francis Pharcellus Church, until nine years later, after he died. Readers kept it instead: by 1930 The Sun was mailing out 163,840 copies of it on request.
Two things that almost did not survive, one as a scrap on somebody else's exam paper, one as a letter that had been mislaid for weeks. Both landed on a 21st of September. Both outlived the hands that made them.
The margin keeps doing this. What gets written in the leftover space, on paper that belongs to something else, keeps outlasting the main text.