Tianyujing neizhuan 天玉經內傳 "Inner commentary on the classic of celestial jade" is a book on geomancy (fengshui 風水), according to legend compiled by the Tang-period 唐 (618-907) master Yang Yunsong 楊筠松 (834-900), who also authored the book Hanlongjing 撼龍經.
The book is not included in Song-period 宋 (960-1279) bibliographies. This circumstance is explained by the story that Yang refused to publish the book during his lifetime, and later appeared to the Song period master Wu Kecheng 吳克誠 to whom he revealed the text. Wu's son Wu Jingluan 吳景鸞 (d. 1046) analysed its meaning and published a kind of commentary called Tianyujing waizhuan 天玉經外傳 "Outer commentary to the classic of celestial jade". The received text of the Neizhuan is 3-juan-long, the Waizhuan 1 juan. It seems that the book was in fact written during the Song period and was only attributed to the honourable geomancy master Yang from the Tang period.
The Neizhuan explains how auspicious spots in the landscape could be found with the help of the Five Agents (wuxing 五行), the Eight Trigrams (bagua 八卦), the Nine Planets/Stars (jiuxing 九星), and the Celestial Stems and Terrestrial Branches (ganzhi 干支, see calendar).
The first part of the book divides the empire in different zones. The region of Jiangdong 江東 is related to the Heavenly Trigrams (tiangua 天卦). The four Yang Stems jia 甲, bing 丙, geng 庚, and ren 壬 had a positive influence on life in this region because they were related to Heaven and to odd numbers. The "eight deities" (bashen 八神) of this region were bestowed the number One. The region of Jiangxi 江西 was related to the Earthly Trigrams (digua 地卦). The Four Yin Stems yi 乙, ding 丁, xin 辛, and kui 癸 had a positive influence on life in this region because they were related to the Earth and to even numbers. The eight deities of this region were bestowed the number Two.
The northern and southern regions as the third part of the empire are not dealt with in the same manner. Their eight deities are bestowed trigrams with the statement that their endpoints were not to show any discrepancies (zhuandi ying wucha 端的應無差).
In the last paragraphs of the first part, the 24 "dragon deities" (longshen 龍神) are also dealt with according to three different trigrams. The trigrams of Heaven, Earth, and the parents, as well as the relation of all these trinities to the Five Agents, are also explained.
The second part of the book deals with 24 different shapes of mountains and the positions of auspicious and inauspicious "cavities" (xue 穴, i.e. "lairs where energies are accumulated") in their surroundings. These could be found out with the help of the Eight Trigrams and the Nine Planets/Stars and their positive or negative constellation to each other, as well as by the order of the Stems and Branches.
The third and last part of the book, which is also called Tianyujing waipian 天玉經外篇, explains the influence of mountains on the course of waters, as well as the relation between the energies Yin and Yang and the Eight Trigrams, and that of the Five Planet gods to the Stems and Branches. The Waipian correlates the Stems, Branches and Hexagrams directly with four of the Five Agents.
|子寅辰 zi, yin, chen
|乾 qian "Heaven"
|丙乙 bing, yi
|金 jin "metal"
|午申戌 wu, shen, xu
|坤 kun "Earth"
|壬辛 ren, xin
|木 mu "wood"
|卯巳丑 mao, si, chou
|艮 gen "mountain"
|庚丁 geng, ding
|水 shui "water"
|酉亥未 you, hai, wei
|巽 xun "wind"
|甲癸 jia, kui
|火 huo "fire"
The four trigrams qian 乾, kun 坤, gen 艮, and xun 巽 are called "Trigrams of the Mysterious Vanity" (xuankonggua 玄空卦). The text stressed the importance to detect "cavities" in the landscape, but not the methods how this was done. The text seems therefore quite imperfect in this section and is hard to comment on.
The language of the Tianyujing is very obscure and in many places not yet sufficiently explained. The whole text is accompanied by an old commentary that provides some help for unclear passages. In spite of its very theoretical and complex character the Tianyujing became one of the classics of geomancy. It is included in the series Dili daquan 地理大全 and Siku quanshu 四庫全書.