Official costume in imperial China was highly regulated, and the decorative motifs of court costumes were specific to rank. Among the emblems employed for the emperor's ceremonial robes were the twelve imperial symbols, as seen on this example: sun, moon, constellation, mountain, pair of dragons, bird, cups, water weed, millet, fire, ax, and the symmetrical "fu" symbol. A bright yellow was reserved for the emperor, but for occasions such as ceremonies performed at the Altar of Heaven, the requisite color was blue. The garment worn for the actual rituals was the more formal court robe ("chao pao"). The dragon robe ("qi fu") was used for the periods of fasting that preceded the ceremony.Except for a few details in black, white, and pale blue silk, this robe is embroidered in very fine gold and silver threads, which are laid in pairs and couched. Besides the imperial symbols, the dragon robe required additional motifs: nine large dragons rendered full face or in profile; and clouds, waves, and mountains symmetrically arranged to represent an orderly universe. This example is further embellished with auspicious "wan" and "shou" medallions, Buddhist and Daoist symbols, and bats.