three old high-crowned hats
Note by H. Craik to chapter 4 of Tale of a Tub

The triple tiara of the Pope. The rest of the sentence refers, of course, to the keys of St. Peter, and the fisher's ring. These, and the very obvious allusions which follow, shew us Swift's humour descending into burlesque. The contrast between such fooling and the more true and wide-reaching humour of the rest of the book, is striking enough.