alchemy with different methods, including visualization, breathwork, ecstatic trance, and sexual practices. In the late Imperial period, neidan developed into complex systems which drew on numerous elements, including: classic Daoist texts and meditations, yangsheng, Yijing symbology, daoist cosmology, external alchemy concepts and terms, Chinese medicine, and Buddhist influences. Neidan systems tend to be passed on through oral master-disciple lineages and to often be secret. Livia Kohn writes that the main goal of internal alchemy is generally understood as a set of three transformations: "from essence (jing) to energy (qi), from energy to spirit (shen), and from spirit to Dao." Common methods for this include conserving the subtle essences (often through celibacy or sexual practices), engaging the subtle body and activating the microcosmic orbit. Komjathy adds that neidan seeks to create a transcendent spirit, usually called the "immortal embryo" (xiantai) or "yang spirit" (yangshen). Texts Some religious Daoist movements view traditional texts as scriptures considered sacred, authoritative, and binding, as well as divinely inspired or revealed. Perhaps the most influential texts are the Daodejing and the Zhuangzi. Daodejing Throughout the history of Daoism, the Daodejing has been a central text, used for ritual, self-cultivation, as well as philosophical purposes. According to legend, the Daodejing (Scripture of the Dao and its power, also known as the Laozi) was written by Laozi. Authorship, precise date of origin, and even unity of the text are still subject of debate, and will probably never be known with certainty. The earliest manuscripts of this work (written on bamboo tablets) date back to the late 4th century BCE and these contain significant differences from the later received edition (of Wang Bi c. 226–249). Apart from the Guodian text and the Wang Bi edition, another alternative version exists, the Mawangdui Daodejings. Luis Komjathy writes that the Daodejing is "actually a multi-vocal anthology consisting of a variety of historical and textual layers; in certain respects, it is a collection of oral teachings of various members of the inner cultivation lineages." Meanwhile, Kirkland argues that the text arose out of "various traditions of oral wisdom" from the state of Chu that were written, circulated, edited and rewritten by different hands. He also suggests that authors from the Jixia academy may have been involved in the editing process. The Daodejing is not organized in any clear fashion and is a collection of different sayings on various themes. The leading themes of