Huang Ting Jing 黄庭經 was written around the time 22-589, during the Wei Jun Southern Northern Dynasty魏南北朝. Huang 黄 means yellow. in the Five Elements yellow is the Earth element and the Centre. East is wood, South is fire, West is metal and North is water. Ting 庭 means land of place. Jing 經 means scripture or classic book. So Huang Ting Jing 黄庭經 means Centre Place Scripture.
It is a classic Daoist book about how to live longer and eventually become Immortal. it covers Qi and works on the three Dantians 丹田. It says the Upper Dantian 上丹田 is found in the forehead between the eyes and relates to the brain. The Middle Dantian 中丹田 is found at the centre of the body at the Tanzhong (Shenzhong) 膻中 and relates to all the internal organs such as the heart, lungs, liver, spleen etc. The Lower Dantian 下丹田 is 3 Cun (which is four finger widths) below the navel, at the Guanyan 關元 point and relates to our kidneys and energy. This is different to what we usually think as we consider the Lower Dantian to be at the Qihai 氣海 point. It also mentions breathing and breathing through the Dantian. It opens up the Ren Mai 任脉 and the Ren Mai smooths the Du Mai督脉. It says saliva needs to be swallowed to nourish the organs like watering the plants. So the Huang Ting Jing was a Daoist knowledge and health book. It helped Chen Wang Ting 陳王廷 create Taijiquan which is good for health and Kung Fu