II. His Ruling Symbols from The Philosophy of Shelley’s Poetry in Ideas of Good and Evil by William Butler Yeats.

“Cythna in the passage where she speaks of making signs ‘a subtle language within language’ on the sand by the ‘fountain’ of sea water in the cave where she is imprisoned, speaks of the ‘cave’ of her mind which gave its secrets to her, and of ‘one mind the type of all’ which is a ‘moveless wave’ reflecting ‘all moveless things that are'” [via]