Della Porta was the most accomplished cryptographer of the Renaissance. This work includes a set of movable cipher disks to code and decode messages. A cipher disk is a paper rotating wheel attached to the page by a piece of string. The cipher disk, or code wheel, rotates to align corresponding characters for the code on the inner and outer dials.
The 1563 Naples imprint on the title page is fictitious. The book was actually published in London in 1591 by John Wolf. Scholars find this work interesting as a clue to possible cryptographical aspects of Shakespeare’s plays.