I have, for quite some time, wanted to read The Toilet Papers: Recycling Waste and Conserving Water by Sim Van der Ryn. A few months ago I picked up a copy, and just finished reading it.
The Toilet Papers, along with Joseph Jenkins' The Humanure Handbook, is one of the books most often suggested for information on alternative methods for the handling and treatment of human waste. While some of the information was dated, having been originally published in 1978, I found that the frequent recommendations were spot on. This is certainly a must read for anyone interested in the idea of humanure composting.
Amazingly, in spite of being just 122 pages long, the book not only covers the topic of human waste, but also of gray water systems and specific toilet designs. The chapter on the "Notes on the History of Easing Thyself" describes some of the various toilets in use throughout history, and explains how we ended up with the modern, water based system, that we have today.
Rather than go into more detail about the information provided in the book, I am just going to recommend that you pick up a copy and read it for yourself. Its a quick, and enjoyable read, while at the same time being very informative. Even if you have no intention of ever using anything other than a traditional toilet, it is likely you'll find some tidbit of interesting information, such as the benefits of relieving oneself while squatting, rather than sitting.