The majority of medieval simple-substitution ciphertexts that I've seen can be learned in about 20 minutes. After that, it's just a matter of writing as though you are using a different alphabet (similar to learning Russian or Greek alphabets and then writing your text with those shapes rather than Latin shapes). In fact, quite a few of them have shapes in common with the letter they are substituting, which makes it even easier to remember (this appears to be deliberate). After c. 1500 things get more complicated, but in the early 15th century, ciphers are pretty simple.
I did see an interesting cipher from the Jewish Kabbalah community that was probably inspired by magic squares, where the alphabet was portioned three characters to the square, but when I played with it (and variations of it), I couldn't find a configuration that resulted in text that was strongly positional, as is the VMS.
The VMS is significantly different from substitution ciphers. It has many regular patterns but, within that, there is a certain level of "something" extra. I'm reluctant to call it sophistication, but it does not appear to be random. Measured and planned might be a better way to describe it. It diverges just enough from preceding patterns to suggest there is something more to it than grilles or magic squares or similar pluck-your-text methods.
I did see an interesting cipher from the Jewish Kabbalah community that was probably inspired by magic squares, where the alphabet was portioned three characters to the square, but when I played with it (and variations of it), I couldn't find a configuration that resulted in text that was strongly positional, as is the VMS.
The VMS is significantly different from substitution ciphers. It has many regular patterns but, within that, there is a certain level of "something" extra. I'm reluctant to call it sophistication, but it does not appear to be random. Measured and planned might be a better way to describe it. It diverges just enough from preceding patterns to suggest there is something more to it than grilles or magic squares or similar pluck-your-text methods.