I’ve discovered that the Internet Sacred Text Archive hosts a decent collection of ethnographic works dealing with American Indian religions and oral traditions. Scanning the available titles, I see works by Franz Boas, Alfred Kroeber, C. Hart Merriam, Edward Sapir, Constance Goddard DuBois, Julian Steward, Frank Cushing, James Mooney, and a number of other well respected and careful researchers. This looks like it’s going to be a lot of fun to explore.