Voynich Manuscript: With the obsessiveness of Adolph Wölfli, the beauty of medieval illuminated manuscripts, and the schematic wonder of Paul Laffoley, the Voynich Manuscript is a stunning work of art. But it's also an unsolved mystery:

In 1912, the antiquarian book dealer Wilfrid M. Voynich bought a number of mediaeval manuscripts from an undisclosed location in Europe. Among these was a lavishly illustrated manuscript codex of 234 pages, written in an unknown script.

Voynich took the MS to the United States and started a campaign to have it deciphered. Now, almost 100 years later, the Voynich manuscript still stands as probably the most elusive puzzle in the world of cryptography. Not a single word of this 'Most Mysterious Manuscript', written probably in the second half of the 15th Century, can be understood.

Details from the manuscript here. (Via Cabinet.)