Hanlongjing 撼龍經 "Classic of shaking the dragon" is a book on geomancy attributed to the Tang-period 唐 (618-907) master Yang Yunsong 楊筠松 (834-900). The book has a length of only 1 juan, but all editions include two lengthy appendices, namely the text Yilongjing 疑龍經 "Suspecting [the presence] of dragons", and the Zangfa daozhang 葬法倒杖 "Methods of burial and the reverse staff".
Yang Yunsong, actually called Yang Yi 楊益, courtesy name Shumao 叔茂, style Yunsong 筠松, probably hailed from Baozhou 寶州 (in modern Shaanxi) and served as a Grand Master of Splendid Happiness (guanglu dafu 光祿大夫). It is said that during the rebellion of Huang Chao 黃巢 (835-884), he profited of the general chaos and stole the text Yuhan mishu 玉函秘術 "Secret art of the jade case" from the palace library. He later arrived in Chuzhou 處州, where he became a disciple of Zeng Wenchan 曾文辿 (854-916). The official dynastic histories do not include a biography of Yang Yunsong. His name is first mentioned in the Song-period 宋 (960-1279) bibliography Zhizhai shulu jieti 直齋書錄解題. The imperial bibliography Yiwen zhi 藝文志 in the history Songshi 宋史 calls him Yang Jiupin 楊救貧. It is said that apart from the Hanlongjing, he also wrote the books Qingnang aoyu 青囊奧語 and Tianyujing neizhuan 天玉經內傳. Yet his authorship of none of these texts can be ascertained.
The book Hanlongjing is specialised on the interpretation of mountain shapes as the vital dragon to be detected in the art of geomancy. It is divided into nine chapters that include a main text and an interpretive part. The method is to identify auspicious spots with the help of certain stars.
The book Yilongjing is divided into three parts, the first of which is dedicated to the search of "branches" (zhi 枝) out of the "stem" (gan 干) with the help of waters. The second part explains the method to detect the head and back of dragons, and the last part describes the connection of "cavities" (xue 穴), in which the energy (qi 氣) of the earth concentrated. For this purpose, it includes ten questions (Yilong shi wen 疑龍十問) about the search of dragon lairs with the help of cavities.
The second appendix, the text Zangfa daozhang, elucidates the relations of such holes to the earth. The "Method of burial" (Zangfa 葬法) is divided into the four chapters Shi taiji 識太極 "Identifying the utmost extreme", Fen liangyi 分兩儀 "Separating the two powers (Yin and Yang)", Qiu sixiang 求四象 "Searching the four phenomena", and Bei bagua 倍八卦 "Doubling the eight trigrams" (see Yijing 易經).
The second part of the book, the "Reverse staff" (Daozhang 倒杖) is a more detailed explanation of the method to determine the place of a tomb, and describes twelve different methods of "staffs" (daozhang shi'er fa 倒杖十二法). It has a short appendix of twenty-four further methods to recognize auspicious and inauspicious places at "gravels" or hills (Ershisi sha zang fa 二十四砂葬法).