Mysterious Principles of the Blue Bag

Padma Sambhava in the Palace of the Glorious Copper Mountain Paradise, late 18th to early 19th century
Chinese maps are drawn with the south at the top. This is the direction you should face in order to comprehend the landscape: then the Green Dragon of the east is at your left hand, which is Yang, and the White Tiger of autumn is at your right, which is Yin. In front of you the sun will be at its zenith, and behind you there is the darkness of winter.
A mountain is Yang also, and so are large rocks, steep waterfalls, age-old pines. It is most Yang on its sunny side, and Yin in its own shadow; and Yin also comprises what is low, cavernous, in a valley, and boggy. If you are looking for a place to build a house or bury your ancestors, you should therefore go to a south-facing slope, with the Green Dragon animating the landscape to your left, and the White Tiger prowling harmlessly (because harmoniously) to your right, and these two should enclose the site as if by the crook of an elbow. At your front there should be a body of water.
The physiognomy of a landscape is so complex that you cannot be sure of your ground without the help of a feng-shui diviner, who understands how every part of it is animated by breath. Feng-shui, wind and water, bespeaks the two most obvious constituents of dragon's breath; for the others the diviner needs a magnetic compass. This may have as many as thirty-eight concentric rings about the needle, each divided into one of the ideal measures of space and time. Using this, the diviner takes sights on the veins of the dragon, which are the raised features of the landscape, noting the watercourses, the trees, rocks, and branching of valleys; and should they fall upon an auspicious setting, a house built there will make its owner prosperous, and ancestors buried in that place will bless their descendants.
Such a site is called the Dragon's Head, and it should be consecrated with offerings in the shape of a dragon; and when the house is built, the dragon is invited to make its abode in a special niche. A garden may also be laid out, a private world of yin-and-yangeries where the dragon may lovingly disport; and it can further be honored with figures of itself to be reminded of its good fortune.
Feng-shui diviners are themselves credited with dragonish powers, not only because they can discern dragons but because they can influence them according to the principles of the Blue Bag, which is their name for the universe. They are largely responsible for the finest use of the landscape the world knows, for the same reasons that Chinese landscape painting has the oldest and richest tradition of its kind.