From Oriental Secrets of Graceful Living (1966), by Boye De Mente:

Up until Rikyu’s time, the Tea-Men taught a high standard of refinement and graceful living. But it was a style of life demanding luxury and leisure. It was not only beyond the reach of the poor but did not contain many of the other elements essential for a true religion. Rikyu added these elements. They were: a unified view of man and nature, and complete spiritual contentment obtained by harmoniously blending everyday life with reality. Those who followed the Way of Tea were promised a long life unmarred by ill health and worries, and when their time came they would be able to accept death calmly and contentedly. As an exercise in aesthetics, the tea ceremony is all inclusive. It teaches the way to perfect understanding of beauty, and once the Teaist reaches this goal, provides a means for him to exercise his new-found understanding on the highest level. Philosophically, the Way of Tea teaches man to recognize and accept his relation with nature, to have respect for all nature including his fellow human beings, to be pure of mind and to behave quietly.