The Magical Seal is a kind of Magical Instrument ( 法器 Faqi ) often used in Daoist rituals of Fasts and Offerings ( 齋醮 Zhaijiao ). Seals were used quite early in ancient China. The Interpretations of the Terms ( 釋名 Shiming ) says, "seals are tokens, so they are used for closing things to authenticate them. Seals are also things to rely on, and they are used for closing things and used as evidence for delivery". Seals should be regarded as a sign to check upon delivery. In ancient times, seals were differentiated according to their ranks. During the Warring States Period, seals used by sovereigns were called Imperial Seals and those used by subjects were just called seals. The Ancient Rituals of the Han Dynasty ( 漢舊儀 Han Jiuyi ) says that the seals of dukes are made of gold with camel-shaped loops and are called Xi in literary language; the seals of counts are made of gold with tortoise-shaped loops and are called Yin in literary language; the seals of prime ministers and generals are made of gold with tortoise-shaped loops and are called Zhang in literary language; the seals of two-thousand dan middle officials are made of silver with tortoise-shaped loops and are called Zhang in literary language; the seals of one-thousand, six-hundred and four-hundred dan officials are made of copper with nose-shaped loops and are called Yin in literary language. After the Song dynasty, seals were classified into gold seals, gold-plated seals and silver seals. The Inscriptions on Seals ( 印銘 Yinming ) by Ge Xuan of the Jin dynasty says that seals can "win the trust of other countries and take sundials as their model. The inscriptions on the seals are clear and concise". It is said that when the Five Pecks of Rice Tradition ( 五斗米道 Wudoumi Dao ), one of the early Daoist sects, divided the region of Ba and Shu into 24 Dioceses, the first Celestial Master ( 天師 Tianshi ) Zhang Daoling used the "Seal of the Chief Official of Yangping Diocese" ( 陽平治都功印 Yangpingzhi Dugong Yin ), which functioned as the seal of the government offices. Seals began to be used in rituals of Fasts and Offerings in the Southern and Northern Dynasties. The types and content of seals gradually grew in number with the increase in the types of rituals. The "chapter on seals of the Numinous Treasure" in The Highest Clarity Numinous Treasure Golden Book of the Great Achievement of Aid and Salvation ( 上清靈寶濟度大成金書 Shangqing Lingbao Jidu Dacheng Jinshu ) of the Ming dynasty collects 46 kinds of seals often used in rituals, such as the "Seal of the Great Magician of the Numinous Treasure" ( 靈寶大法師印 Lingbao Dafashi Yin ), the "Seal of the Mysterious Altar of the Numinous Treasure" ( 靈寶玄壇印 Lingbao Xuantan Yin ), etc.