Art of the Tea Ceremony
Tea ceremony developed as a "transformative practice," and began to evolve its own aesthetic, in particular that of wabi. Wabi, meaning quiet or sober refinement, or subdued taste, "is characterized by humility, restraint, simplicity, naturalism, profundity, imperfection, and asymmetry [emphasizing] simple, unadorned objects and architectural space, and [celebrating] the mellow beauty that time and care impart to materials" ("Introduction: Chanoyu, the Art of Tea" in Urasenke Seattle Homepage.) Ikkyu, who revitalized Zen in the 15th century, had a profound influence on the tea ceremony.
The above excerpt is from the Wikipedia article, "Japanese tea ceremony".