Thanks for the comments. I thoroughly enjoyed Between Silk and Cyanide. A small correction, the Playfair is actually a substitution cipher (mapping diagrams to diagrams) not a transposition cipher. The Playfair is a paper and pencil cipher that can usually be broken by hand with even modest amounts of material[1]. The Playfair (and the Wheatstone bridge) were invented by Sir Charles Wheatstone.
[1] Helen F. Gaines, Cryptanalysis, chapter 21. https://www.amazon.com/Cryptanalysis-Study-Ciphers-Their-Sol...