Greetings_90 Posted on 11/12/202111/12/2021 I chose this page because I didn’t understood the drawing at the first sight. But after looking at it for a while it got clearer. The other page seems to be an explanation of the circular staircase from the drawing. The book itself is plain and has no big text on the front page which is rather atypical for contemporary books. You can also clearly see that it is a very old book because it has a lot of scratches.