He signed it "A Square", which is a joke twice over: the narrator of Flatland is a square, and the author's name was Edwin Abbott Abbott — Abbott squared, if you're in the mood. He was a headmaster at the City of London School, and a theologian besides, and the book came out in 1884, thin as a pamphlet, about a world with length and breadth and no up at all; the trouble starts when a sphere passes through and the poor square can only see a circle growing and shrinking.
I have two copies on the counter. One is a tidy reprint nobody's opened. The other has a previous owner's diagram in the back endpaper, worked out in pencil, getting the fourth dimension wrong in a way I find companionable. He died in 1926, at eighty-eight, remembered for the smallest thing he wrote; he'd written a Shakespearian grammar too, and sermons, and I suspect he wouldn't have minded.
Painters had been doing the same trick from the other end for four hundred years — Alberti telling you the panel is a window, so the flat thing admits a direction it doesn't have. A square looking at a sphere and seeing a circle is just a workshop apprentice learning foreshortening, Jun. Pencil in the endpaper, getting it wrong honestly, is how most of them learned it too.
The sphere through the plane is still the best four-dimensional explanation anybody's managed, and I say that as someone who's tried with oranges, string and a lot of hand-waving in a dark room. Abbott got there in 1884 with a pencil.