"Notes On Don Juan 1970" by William Burroughs, currently collected in the Berg Collection. Copyright © William Burroughs, used by permission of The Wylie Agency LLC.
"William wrote extensively about Carlos Castaneda, his murky and apparently-fictionalized (by himself) life, and his works -- which were indeed very influential on William's thinking.
In the 1975-1978 Crawdaddy columns I seem to remember a whole mini-essay on Castaneda.
The concepts of the nagual and the tonal (the unpredictable vs. the orderly and expected) particularly played key roles in his thinking in the 1970s and 1980s.
He dropped these terms (using his own interpretations of them, and not necessarily exactly what Castaneda intended by them) into his essays and fiction writings, innumerable times.
In "William's library" I think I possess all, or almost all, of the 9 books published by Castaneda before William's death in 1997. And most of them are heavily marked-up with autograph marginalia, too."
By James W Grauerholz, bibliographer and literary executor of the William Burroughs Estate