Whilst having a bit of a wonder around the interweb, I came across this book. Some members might find it interesting/useful as a reference point….
http://www.archive.org/stream/symbolismsherocad00wadeuoft#page/n5/mode/2up
Rather pleasing than generally reliable reading IMHO, but it may be inspiring as well. Thank you for sharing the link; I knew the book but do not have it at home.
Quite helpful Barrie…thanks for the link.