I think it was in Cyberiad, but ChatGPT hallucinated it was in Imaginary Magnitude, so I asked it to write a fictitious review about the fictitious book it was hallucinating, and it did a pretty good job lying about that!
It did at least come up with (or plagiarize) an excellent mathematical Latin pun:
"I think, therefore I sum" <=> "Cogito, ergo sum"
[1] I think Doug Hofstadter's original formulation was "I think, there for I sum" <=> "Cogito, ergo think", therefore I sum... [2]
[2] "To paraphrase Descartes again: “I think; therefore I have no access to the level where I sum.”" ― Douglas R. Hofstadter, Gödel, Escher, Bach: An Eternal Golden Braid [1]
ChatGPT> The book, filled with esoteric references to imaginary works and pseudo-scientific jargon, is a delightful exercise in intellectual gymnastics. One particularly memorable chapter, consisting entirely of binary code, is later revealed to be an in-joke—when decoded, it simply reads, "I think, therefore I sum."
[...]
ChatGPT> Firstly, the phrase is a play on René Descartes' famous philosophical statement, "Cogito, ergo sum," which translates to "I think, therefore I am." Descartes used this statement to assert that the act of thinking is proof of one's own existence and consciousness. In my adaptation, "I think, therefore I sum," there's a witty twist where 'sum' refers both to the act of summing or calculating, a fundamental operation in computing, and to the philosophical concept of existence or being.
Full transcript:
https://chat.openai.com/share/9a9e9818-1e23-488e-b517-6d23e3...
... a very good book, by the way.