What strikes me is ... The drawings aren't very good. They are at my sort of level (OK a bit better). But in terms of modern professional illustrators ... They are childish.

It's amazing just how far we have come.

And worth noting anyone educated enough to read and write, obsessed enough to create a whole book (even today that's an acheievement) is not going to be a well balanced thoughtful kind. Hence, manuals of black magic with badly drawn picture...