Here's the account in his own words, including the famous quote:
"Paige and I always meet on effusively affectionate terms, and yet he knows perfectly well that if I had him in a steel trap I would shut out all human succor and watch that trap till he died."
Another line:
"In one contract he got me to assign to him several hundred thousand dollars’ worth of property ... said valuable consideration being the regiving to me of another piece of property which ... already belonged to me! I quite understand that I am confessing myself a fool; but that is no matter, the reader would find it out anyway as I go along."
https://standardebooks.org/ebooks/mark-twain/the-autobiograp...