Inside the weird and delightful origins of the jungle gym, which just turned 100

https://www.npr.org/2023/11/08/ [login to see] /jungle-gym-playground-monkey-bars-maths-hinton-fourth-dimension
This story starts in the fourth dimension.

Or, more specifically, with a British mathematician who, in the late 1800s, was intrigued by the fourth dimension and how to teach disinterested children about it.

Charles Hinton wore a lot of hats. He wrote sci-fi stories before there was sci-fi — he called them "scientific romances." At Princeton, where he worked for a time as mathematics instructor, he invented a baseball pitching machine powered by gunpowder. He also practiced polygamy, which was against both the mores and laws of his native England. And when he was convicted of bigamy in the 1880s, he was forced to move his young family to Japan where he found work teaching mathematics.