"The Divina Commedia contains a large number of cryptograms which have never, so far as I know, been noticed…. A cryptogram, or hidden writing, is a deliberate arrangement of words, letters, numbers, or other signs, which is intended to conceal as well as express a meaning…. Among the cryptograms which I have discovered in the Divina Commedia are acrostics, telestics, interior sequences, anagrams, irregular letter clusters, string ciphers, and cabalistic spelling devices.
I am far from assuming that the cryptograms which I have discovered are all that Dante made…. The announcement that the Divina Commedia is teeming with cryptograms is likely, I am aware, to be met with incredulity."
–Walter Arensberg, The Cryptography of Dante (1921)