predating the Maoshan () revelations. Taoist generally do not consult published versions of the Daozang, but individually choose, or inherit, texts included in the Daozang. These texts have been passed down for generations from teacher to student. The Shangqing School has a tradition of approaching Taoism through scriptural study. It is believed that by reciting certain texts often enough one will be rewarded with immortality. Symbols and images The Taijitu (; commonly known as the "yin and yang symbol" or simply the "yin yang") and the Bagua ("Eight Trigrams") are important symbols in Daoism, since they represent key elements of Daoist cosmology (see above). Many Daoist (as well as non-Daoist) organizations make use of these symbols and they may appear on flags and logos, temple floors, or stitched into clerical robes. According to Song dynasty sources, it originated around the 10th century CE. The tiger and dragon are more ancient symbols for yin and yang respectively, and these two animals are still widely used in Daoist art. Daoist temples in southern China and Taiwan may often be identified by their roofs, which feature dragons, tigers, and phoenixes (with the phoenix also standing for yin) made from multicolored ceramic tiles. In general though, Chinese Daoist architecture lacks universal features that distinguish it from other structures. Daoist temples may fly square or triangular flags. They typically feature mystical writing, talismans or diagrams and are intended to fulfill various functions including providing guidance for the spirits of the dead, bringing good fortune, increasing life span, etc. Other flags and banners may be those of the gods or immortals themselves. Drawings of the Big Dipper (also called the Bushel) are also important symbols. In the Shang Dynasty of the 2nd millennium BCE, Chinese thought regarded the Big Dipper as a deity, while during later periods it came to symbolize Taiji. A related symbol is the flaming pearl, which stands for the pole star and may be seen on such roofs between two dragons, as well as on the hairpin of a Celestial Master. Symbols which represent longevity and immortality are particularly popular, and these include: cranes, pine trees, and the peaches of immortality (associated with the goddess Xiwangmu). Natural symbols are also common, and include gourds, caves, clouds, mountains and the animals of the Chinese zodiac. Other symbols used by Daoists include: the Yellow River Map (hetu), the Luo Sho square, Yijing coins, Daoist