Qingnang aoyu 青囊奧語 "Secret words of the Green Bag" is a short book on geomancy (fengshui 風水). In all editions it is accompanied by the text Qingnangxu 青囊序 "Introduction to the [treatise] on the green bag". Both are also called Qingnangjing 青囊經 "Classic of the Green Bag". Authorship of the Qingnang aoyu is traditionally attributed to the Tang-period 唐 (618-907) scholar Yang Yunsong 楊筠松 (834-900), who also wrote the geomantic book Hanlongjing 撼龍經.
The Qingnangxu is said to have been compiled by Yang's disciple Zeng Wenchan 曾文辿 (854-916), who hailed from Ganshui 贛水 in modern Jiangxi and was himself a teacher of the famous Daoist master Chen Tuan 陳摶 (871-989). Yang Yunsong's book explains the relation between the "energies" Yin and Yang 陰陽 and the illumination of the nine stars/planets (jiuxing huayao 九星化曜), the qualities of mountains and waters for the construction of buildings, and the auspicious and non-auspicious relevance of "cavities" (xue 穴, i.e. "lairs" where positive energies are accumulated) in the landscape.
It provides 24 examples of mountains and waters whose positive or negative influence could be reverted, how "precious cavities" (baoxue 寶穴) were to be found, and where "fire pits" (huokang 火坑) might be found. It explains the "woofs and warps" of the golden dragon (jinlong jingwei 金龍經緯), and the productive and destructive change of vital or lethal energies (qi 氣). Each mountain could be analysed according to five directions, in which life was blossoming or withering, and on which the starry constellations had a positive or negative influence.
The Qingnangxu is a kind of explanatory postface (xu 序) to the Qingnang aoyu. It enriches the theory of the 24 mountain shapes by the theory of female and male dragons that add to the "wonderful-mysterious regime" (xuanmiao zhi li 玄妙之理) of Yin and Yang in certain places. In imitation of the Shuogua 說卦 "Explaining the hexagrams" part in the divinatory classic Yijing 易經 "Book of Changes", Zeng Wenchan develops the theory of positive and negative influence of Yin and Yang and brings forward a mantic calculation pattern with the help of the Terrestrial Branches (tiangan 地支, see calendar), with the order hai 亥, mao 卯, wei 未, yin 寅, wu 午, xu 戌, si 巳, you 酉, chou 丑, shen 申, zi 子, and chen 辰. These twelve Branches are divided into four "camps" (ju 局) and multiplied to 48 camps, in which Yang encroaches from the left side, and Yin turns in from the right side. Zeng stresses the importance of finding out the flourishing spots in the landscape.
The Qingnangjing had a great influence on later writings on geomancy and landscape astrology, for instance, the Song-period 宋 (960-1279) books Tiangyujing waizhuan 天玉經外傳 and Sishiba ju tu 四十八局圖 by Wu Kecheng 吳克成 and his son Wu Jingluan 吳景鸞 (d. 1046), or the Yuchijing 玉尺經 by Liu Bingzhong 劉秉忠 (1216-1274). It is nevertheless hard to say which parts are originals from the Tang period, and which were added later. The concept of the couples fortune-misfortune (jixiong 吉凶), mischief-luck (huofu 禍福), prosperity-decline (rongru 榮辱), or valuable-worthless (guiqian 貴賤), used in geomancy, seem to be a younger invention.