could be calculated. The six ding are the spirits who are responsible for the position of the irregular gate (), which represents a rift in the universe. The irregular gate must be approached by performing the paces of Yu and serves as the entrance to the emptiness of the otherworld in which invisibility to evil influences is achieved. The Beidou Zhifa Wuwei Jing () states that Jiutian Xuannü taught the method to mobilize the stars of the Northern Dipper to Yuan Qing (), an official during the transition from the Sui to the Tang dynasty. The method is known as Beidou Shi'er Xing (, translated "Twelve Stars of the Northern Dipper"). The Shangqing Tianxin Zhengfa (), produced in the Southern Song period, gives an incantation entitled Tiangang Shenzhou (, translated "Incantation of the Heavenly Mainstay") that accompanies the method. Longevity The goddess Jiutian Xuannü appears in several works of physiological microcosmology in which the human body is seen as a microcosm of the universe and where the gods are present within. These texts locate Jiutian Xuannü along the central median of the body and associate her with the circulation of breath, which nourishes the vital spirit and provides longevity. Jiutian Xuannü appears at least three times in the Huangting Jing (), where the adept is instructed to send down his breath to enter the goddess' mouth. The Taishang Laojun Zhongjing (), probably dating to the 5th century, mentions that she is "located between the kidneys, dressed only in the white of Venus and the brilliant stars. Her pearl of Great Brilliance shines to illuminate the inside of the adept's whole body, so that he can extend his years and not die." In the Laozi Zhongjing (), Jiutian Xuannü is described as one of the three deities who are sitting on divine tortoises. The author comments: "The Mysterious Woman is the mother of the Way of the void and nothingness." The text gives instructions to adepts: "Close your eyes and meditate on a white breath between your shoulders. In its centre is a white tortoise. On top of the tortoise is the Mysterious Woman." There are two governors beside her, which adepts are instructed to summon by saying: "Governor of Destiny and Governor of the Registers, pare so-and-so's name from the death list and inscribe it on the Life List of the Jade Calendar." This ritual therefore points to a procedure