John Beal, a London businessman, is given a magic crystal that allows him to go back in time
and change one act; he is happy with his current life, so he decides to merely go back to
catch a train that he was annoyed about missing ten years ago—but the resulting changes are
more than he ever expected.
This is the earliest story that I’ve seen where the hero goes
back into his earlier body and relives something differently. Some of the later stories of
this kind have no actual time travel, but merely give knowledge of an alternate timeline
(e.g., Asimov’s “What If?”); others live out the two timelines in parallel (e.g., the
1998 movie Sliding Doors, also set in motion by a missed/caught train); and some, like
If, are couched in terms of time travel (e.g., the 1986 movie Peggy Sue Got
Married).
— Michael Main
He that taketh this crystal, so, in his hand, at night, and wishes, saying ‘At a
certain hour let it be’; the hour comes and he will go back eight, ten, even twelve
years if he will, into the past, and do a thing again, or act otherwise than he did. The
day passes; the ten years are accomplished once again; he is here once more; but he is
what he might have become had he done that one thing otherwise.