Tan Qiao
The Huashu was originally written by the Daoist Tan Qiao (simplified Chinese: 谭峭; traditional Chinese: 譚峭; pinyin: Tán Qiào; Wade–Giles: T'an Ch'iao; ca. 860 CE-ca. 940 CE), whom Anderson (2007:518) describes as a "shadowy figure".
The 10th-century Xu xian zhuan 續仙傳 "Continued Biographies of Immortals", by Shen Fen 沈汾, has the earliest account of Tan Qiao. He was from Quanzhou (in present-day Fujian) and his Chinese style name (zi 字) was Jingsheng 景升 "Brightness Ascending". His father Tan Zhu 譚洙, who was a director of the Guozijian "Imperial Academy" during the Tang Dynasty (618-907 CE), educated him in the Confucian classics and histories to prepare him for the Imperial examination. Qiao was an excellent student but more interested in the Daoist classics, particularly the hagiographies of xian 仙 "immortals; transcendents". Tan Qiao left home to study Daoism on Mount Zhongnan and never returned. After travelling through the Sacred mountains of China, he lived for a decade on Mount Song 嵩山 (Henan), where Daoist priests taught him neidan alchemical techniques of bigu 辟穀 "abstention from cereals" and yangqi 養氣 "nourishing qi", roughly corresponding with Western practices of inedia and breatharianism. "He wore furs in summer and thin garments in winter, and he would often lie about in the snow and rain, to all appearances dead" (Herbert Giles 1898:710). This compares with the Himalayan tradition of tummo, which is still practiced by the Kagyu school. Tan's father regularly sent him money and clothing, which he promptly spent on wine and gave away. Tan later went south to Mount Nanyue 南岳, or Mount Heng (Hunan), where he allegedly perfected the jindan 金丹 "golden elixir" and could change shape, become invisible, and enter fire or water without being harmed (all Daoist metaphors for xian transcendence). Finally, he travelled to Mount Qingcheng 青城 (Sichuan), where he disappeared.
Some sources confuse Tan Qiao with a more famous Daoist Tan Zixiao; both had the same Chinese surname, both lived in the 10th century, and both traveled in southern China. This mistaken identification began with the Huashu edition in the 1607 CE Daozang supplement Wanli xu daozang 萬歷緒道臧. Its preface notes that Tan Qiao's pseudonym (hao 號) was Zixiao Zhenren 紫霄真人 "Perfected Person of the Purple Clouds/Skies" (Lembert and Schenkel 2002:213 translate "The True Man of the Purple Sky"). Later gazetteers and histories repeated this pseudonym, but Zixiao already referred to another Daoist named Tan.