In January 2021, after watching a documentary on cryptanalyst Elizebeth Smith Friedman, I learned about the online  Friedman Cryptologic Collection at the George C. Marshall Foundation.   

It included images of a 1904 Russian book,  The Enciphered Letter;   A Criticism of the Cipher Systems in Use Among Us. 

I am not a Russian speaker, but for 10 weeks, I typed the Cyrillic into Google Translate to produce an English translation of the book.

It was an interesting experience from many angles:   language, alphabets, machine translation, image processing, character recognition, history, ciphering, and subversion.   

The results and related information can be found here   (link will leave this  web site).