Fascinatingly, such rock gardens go back even further, to Taoist miniature gardens where the rocks represented the isle of paradise, where, far out in the Pacific, the Immortals live, and so back to the legends of Warring States China. The First Emperor sent a number of expeditions east to find the islands; sensibly, they never returned. See the chapter on Chinese alchemy in Mircea Eliade's The Forge and the Crucible, passim.