Ok I know R.E.H was among other things an avid Physical Culturalist/Weight lifter and am myself the same thing and restrict my training methods to the 1800's through 1939 which is before bodybuilding became its own thing and am training using the late George Hackenschmidt's training methods laid out in his book The Way to Live. Anyway I am trying to find out the names of any books and courses on Physical Culture and Weight lifting he might have owned and the names of the Writers of them so I can search out copies of them. Does anyone have any knowldge in this area of R.E.H. history?
The other thing I tried was using Google Ngram. If you Google "Ngram" you will get the search engine for the entire corpus Google has scanned (still only a small percentage of the total number of books). You can use various terms and control the dates before generating a graph. At the bottom of the graph, they will have a link into Google Books for certain time periods, thus giving you potential sources that Howard might have been able to use.
So, for instance, using the term "weight lifting" and 1800-1936, I came up with this: