To Charles Watkins and the List,
When I still held out some hope of making sense of Ada,* I found two books that were helpful on the understanding of gnomon concept:
Sundials: History, Theory, and Practice by René R. J. Rohr and
Gnomon: From Pharaohs to Fractals by Midhat J. Gazale
Carolyn
* there is an L-shaped aspect to the gnomon and the word appears in some of Van's theoretical writings.