It took me a long time to notice that the word in the title is “massage”, and not “message”, in Marshall McLuhan’s and Quentin Fiore’s The Medium is the Massage (An inventory of effects): https://en.wikipedia.org/wiki/The_Medium_Is_the_Massage

Links to various editions: https://www.biblio.com/the-medium-is-the-massage-by-marshall...

Also of interest, notes about the observer being the observed in Jiddu Krishnamurti’s Think on These Things — https://www.biblio.com/9780060916091 — and The First and Last Freedom: https://en.wikipedia.org/wiki/The_First_and_Last_Freedom