early Japanese gardens largely followed the Chinese model, but gradually Japanese gardens developed their own principles and aesthetics. These were spelled out by a series of landscape gardening manuals, beginning with in the Heian Period (794–1185). The principles of sacred gardens, such as the gardens of Zen Buddhist temples, were different from those of pleasure or promenade gardens; for example, Zen Buddhist gardens were designed to be seen, while seated, from a platform with a view of the whole garden, without entering it, while promenade gardens were meant to be seen by walking through the garden and stopping at a series of view points. However, they often contain common elements and used the same techniques. Miniaturisation: The Japanese garden is a miniature and idealized view of nature. Rocks can represent mountains, and ponds can represent seas. The garden is sometimes made to appear larger by forced perspective: placing larger rocks and trees in the foreground, and smaller ones in the background. Concealment : The Zen Buddhist garden is meant to be seen all at once, but the promenade garden is meant to be seen one landscape at a time, like a scroll of painted landscapes unrolling. Features are hidden behind hills, trees groves or bamboo, walls or structures, to be discovered when the visitor follows the winding path. : Smaller gardens are often designed to incorporate borrowed scenery, the view of features outside the garden such as hills, trees or temples, as part of the view. This makes the garden seem larger than it really is. Asymmetry: Japanese gardens are not laid on straight axes, or with a single feature dominating the view. Buildings and garden features are usually placed to be seen from a diagonal, and are carefully composed into scenes that contrast right angles, such as buildings with natural features, and vertical features, such as rocks, bamboo or trees, with horizontal features, such as water. According to garden historians David and Michigo Young, at the heart of the Japanese garden is the principle that a garden is a work of art. "Though inspired by nature, it is an interpretation rather than a copy; it should appear to be natural, but it is not wild." Landscape gardener Seyemon Kusumoto wrote that the Japanese generate "the best of nature's handiwork in a limited space". There has been mathematical analysis of some traditional Japanese garden designs. These designs avoid contrasts, symmetries