I have just bought a collection of books in nudism/naturism but among the parade of boobs and bums the book that I've enjoyed the most is The Fresh Air Book by J. P. Muller, ex-lieutenant in the Danish Army and author of "My System" which, by 1908 when this current book is published, has sold 350,000 copies. Part of the same Physical Culture movement which gave us Eugene Sandow, Mr Kellogg and the Naturist phenomenon, Lt. Muller appears quite a character living with his wife and two young sons in their 'fresh air cottage' in Switzerland.
The Fresh Air Book is full of useful advice on the benefits of air--baths: effectively stripping off and allowing yourself to be bathed by the air or, as we know it today of course, sun bathing. But lots of other healthful advice too with chapter headings such as "The Art of Eating and Fasting", "Concerning Appendicitis", "The Cultivation of Gymnastics" and "How to Lie Abed". The latter, if you are interested is summed up as 1) wide-open windows, 2) absence of sleeping garments, 3) lightness of covering and 4) small pillow - try it tonight.
The book is published by Health and Strength Ltd whose books I have come across before and who publish a catalogue of books on "athletics, physical development, diet, heath, strength and general care of the body." As well as publishing the magazine Health and Strength The National Organ of Physical Fitness. Although this might all seem a little cranky now it's worth remembering that this is were everything we know today such as gyms, jogging, working-out, and body-building have their roots. H+S Ltd included on their list titles such as, The Text Book of Ju-Jitsu,. Fifty Exercises for Health and Strength, Running and Cross-Country Running, Scientific Boxing & Self-Defence and The Eustace Miles System of Physical Culture. One I remember passing through my hands once which had a particularly humorous bent was The Text Book of Club Swinging. The titles of this publisher aren't prohibitively expensive and, although I don't know anyone who has done it, I imagine they would make a really interesting but also achievable collection.