The imagery of your falcon in the gyre isn’t far removed from the imagery of a pern within a gyre. Could Yeats have misspelled pern (spelling it perne)? If just one thinks of Yeats’s perne being a fowl of prey, then Yeats’ is comparing the sages to birds of prey. https://wireless-charger-with-mul08631.blogdon.net/a-review-of-perne-de-c-l-torie-38160985