Murata Jukō is known in chanoyu history as an early developer of tea as a spiritual practice. He studied Zen under the monk Ikkyū, who revitalized Zen in the 15th century, and this is considered to have influenced his concept of chanoyu. By the 16th century, tea drinking had spread to all levels of society in Japan. Sen no Rikyū and his work "Southern Record", perhaps the best-known—and still revered—historical figure in tea, followed his master Takeno Jōō's concept of "ichi-go ichi-e", a philosophy that each meeting should be treasured, for it can never be reproduced. His teachings perfected many newly developed forms in architecture and gardens, art, and the full development of the "way of tea". The principles he set forward—, , , and —are still central to tea. Sen no Rikyū was the leading teamaster of the regent Toyotomi Hideyoshi, who greatly supported him in codifying and spreading the way of tea, also as a means of solidifying his own political power. Hideyoshi's tastes were influenced by his teamaster, but nevertheless he also had his own ideas to cement his power such as constructing the Golden Tea Room and hosting the Grand Kitano Tea Ceremony in 1587. The symbiotic relationship between politics and tea was at its height. However it was increasingly at odds with the rustic and simple aesthetics continuously advertised by his tea master, which the regent increasingly saw as a threat to cementing his own power and position, and their once close relationship began to suffer. Finally in 1590, one of the leading disciples of Rikyu, Yamanoue Sōji, was brutally executed on orders of the regent. One year later the regent ordered his teamaster to commit ritual suicide. The way of tea was never so closely intertwined with politics before or after. After the death of Rikyū, essentially three schools descended from him to continue the tradition. The way of tea continued to spread throughout the country and later developed not only from the court and "samurai" class, but also towards the townspeople. Many schools of Japanese tea ceremony have evolved through the long history of "chadō" and are active today. In the 1906 essay "The Book of Tea", written by the scholar Okakura Kakuzō (1862–1913), chadō is described as follows: It insulates purity and harmony, the mystery of mutual charity, the romanticism of the social order.