Book ID: Man recovers wiped memory (Le Guin) [duplicate]

Question

In a book by Ursula K. LeGuin, a man who knows his memory will be wiped sets up clues he will find and use to gradually recover his memory.

As I recall, the book begins as he “wakes up” and is recalling a poem or lines he has repeated over and over before the wiping. He may find clues in a book he has been allowed to keep, where he has written something to further jog his memory.

I’ve looked through all my paperbacks of hers, but can’t find it.

Answer 1

City of Illusions.

It opens with his memory erased, and he wanders the world until he comes to the Shing, who tell him he's an ambassador, and that rebels erased his memory, which they can restore -- with the destruction of his current memories and personality.

He consents, but tells a character he traveled with to remind him to read his copy of the Tao Te Ching. This restores the memories of when he was amnesiac.