“I did go through [Harr's snare drum book] as a matter of fact. I went to public school in Pontiac, Michigan, so I didn't do anything extra. [...] I didn't have that advantage of being able to take private lessons, so I had to get everything that I had, at least up to that point, for myself. [...] So I got that book and that night I went home and sat over it and pored over it and read it from cover to cover, trying to make some sense out of it. Finally, all of a sudden I understood what it was. I knew exactly what it meant, what all of it (meant) from page one to the back cover. I pondered over that the next day, and so I learned how to do it. In two days, I mastered that book, and the rudiments.”
From an old interview in Percussive Notes— it now appears that you must be a member of PAS to access the archives, and I've let my membership lapse. What an excellent time to renew or join!