Archimedes

Airciméidéas. Translated by Peadar Ó Casaide. Illustrations by Ghislaine Joos. Oifig an tSoláthair. 1979. (Irish. Original Dutch, Desclée De Brouwer, Bruges)

Short illustrated account, for children, of his life and inventions. I liked the cipher idea:
Wrap a ribbon of paper round a rod, in a spiral. Write the message along the stick, unwind and send. The recipient decodes by rewinding it on a rod of the same diameter.
Unless you assume uniform spacing of characters, this cannot be converted to any standard mathematical cipher. But it is rather like the following: (1) Write the message as an m by n matrix of characters, i.e. m rows of n characters. Then transpose the matrix, and transmit the rows one by one.
Easy enough to crack, to be sure. The original version could be a lot more trouble, since the sender can use any old scrawl, abbreviations, variations in calligraphy, and add noise in the form of doodles and dirt. However, careless doodles might assist alignment of the sections, so maybe better not to do that.