query re: Foucault and truth

Dear Foucault List,

I have been a lurker here for several years, without much time to
contribute to the general discussion but certainly enjoying some of what
goes on. A friend of mine has emailed to ask about a passage in Foucault
-- she wants it to quote in a film project. I have a peculiar memory and
just blank out when quizzed about specific images. Does anyone know where
she might look for the quotation that she describes, below?

"do you know where Foucault (or anyone for that matter) writes about truth
as buoyant or light or upwardly inclined. I think the specific passage I'm
remembering (that definitely has left the image of bubbles rising to the
surface in my mind) is somehow in ref to confession and I thought it was
in one of the Hist. of Sexuality volumes (tho I can't find it on first
look). Any suggestions re where to look?"

Thanks a lot for any help you can give her.

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