Wei, the Rooftop of the Black Tortoise

Wei, the Rooftop, is the twelfth of the twenty-eight xiu and the fifth mansion of the northern palace, the Black Tortoise, one of two mansions romanised Wei, this one meaning rooftop or ridgepole. It is identified with stars in Aquarius and Pegasus. In the later astrological tradition its animal totem is the Swallow. As one of the twenty-eight lunar mansions it tracks a segment of the Moon's monthly path. These are the conventions of the Chinese astronomical and calendrical tradition, in which the twenty-eight xiu order the heavens into four palaces of seven mansions each; the Black Tortoise of the north, from Dipper to Wall, gathers the mansions the almanac assigns to the winter quarter of the year.

Wei the Rooftop is one of three separate mansions romanised identically as Wei in the Latin alphabet despite representing three unrelated Chinese characters and meanings, tail, rooftop and stomach; the repetition is purely an accident of romanisation systems that do not mark tone or preserve the original character, and readers working from English-language sources should not assume any connection between the three simply because the transliterated spelling coincides rather than the underlying Chinese writing.