"How was it that a German priest writing in Latin and living in a French city far from the coast became the first person to tell the world that a vast ocean lay to the west of the American continents?"
Wikipedia's collection of "Problems," found while looking at the "List of Unsolved Problems" page and going up a category. These range in seriousness from the "Hat Puzzle" to the "Problem of Evil."
Another image along the same lines as the previous one, this time from an exhibition at the Met.
It's awesome that Irdial are releasing this collection for free. Awesome and mysterious.
More at:
The Conet Project - Recordings of Shortwave Numbers Stations 