The tradition of Japanese gardening was passed down from sensei to apprentice, in a rigorous apprenticeship that has remained unbroken since the fifteenth century. The opening words of Zōen's Illustrations for designing mountain, water and hillside field landscapes (1466) are "If you have not received the oral transmissions, you must not make gardens" and its closing admonition is "You must never show this writing to outsiders. You must keep it secret".[1]
http://en.wikipedia.org/wiki/Japanese_garden