In Dr. Jeff Meldrum’s Sasquatch: Legend Meets Science (New York: Forge Books/Macmillan, 2006), one of the earliest uses of wood knocking to communicate with a Bigfoot/Sasquatch, is cited. According to Meldrum, the original source is contained in a letter from John Green.
The early non-Native wood knocking incident involved Bob Titmus in the Bluff Creek area in 1959. This would have been during his Tom Slick-sponsored work in the area, no doubt, because Art Long was also present.
Below is page 185, from Meldrum’s book, with the specific passage in question: