Raster,
Re: "by noyade" and chapter 29 of THE SWORD OF THE LICTOR. Say more . . . seems to me that chapter 30 might be closer to "by noyade" (i.e., the fate of Severian's captors after he blows up their boat) but even then I had never thought to make the connection between that scene and the brown book.
Uh, oh-DUH. Looking over chapter 29 I see the word itself--Severian is wondering if they will dispatch him via noyade. THIS is what you are talking about! That =is= a curious touchstone . . . noyade being a technical term we might expect a torturer to know, but the editors/writers of the brown book? (Maybe they had a technical consultant?)
"Noyade" is also interesting by itself because it is more modern (Revolutionary France) than medieval when compared with a lot of the other torturing terms used in the Urth Cycle: OED gives "noyade" at circa 1794, first text citation 1822.
Egad, maybe the brown book tale is one from the French Revolution! (In the same twisted way that "The Tale of the Student and His Son" is from the American War Between the States; and how "The Tale of the Boy Called Frog" relates to the early English colonies in North America.)
But anyway, your point being that the brown book at that wind-in-the-leaves moment acts like an oracle (at least), in the same way that the Vatic Fountain works. So then, your challenge <g> is to find a few of the other tidbits, like:
"soulless warrior!"
and
"lucid yellow"
=mantis=