《玄洞玉诏》曰∶昔广成子教黄帝炼外丹，方有铅汞之物，凡以内事为法则也。人之初生，
先生肾也，肾为北方壬癸水，在五金而为铅。次生心也，心为南方丙丁火，在八石而为砂。铅中取银，如肾
气之中暗藏真一之水。砂中取汞，如心气之中暗藏正阳之气。盖以外铅中银而合砂中汞，自然成砂，
火候合宜，锻成大宝。取类于人，则肾气之中，取真一之水；心液之上，取正阳之气。二物合而
为丹，乃如外物见宝之比也。《传道集》曰∶抱天一之质而为五金之首者，黑铅也。铅以生银，铅乃
银之母。感太阳之气而为众石之主者，朱砂也。砂以生汞，汞乃砂之子。难取者，铅中之银；易失者，
砂中之汞。铅汞若相合，锻炼自成宝。此铅汞之理见于外也。若以内言之，父母真气合而为一，即精血
为胞胎，凝结为内
肾。内肾者，铅也。及夫肾中生气，气中生水，以肾水合心液之上正阳之气，凝结于黄庭而为丹。
则曰真铅也。以肾气合心气，积气生液，结为玄珠，方还下丹田而曰汞也。及夫丹就真气升，肾气入顶
而真水降，一升一沉，于十二楼前而为既济。既济一次而还下丹田，故曰真汞也，《元皇君诀》曰∶
铅汞鼎中居，烧成无价珠。都来两个字，了得万家书。正一真人曰∶铅汞传来几万秋，几人悟得几人
修？若教此理常人会，尘世神仙似水流。吕公曰∶金丹一粒定长生，须得真铅炼甲庚。火取南方赤凤
髓，水求北海黑龟精。古今上圣，称说铅汞之理不同，其来止于铅为肾水而真铅为丹，汞为心液
而真汞为药。真铅真汞为既济，若凭外说，不可中理矣。
《玄洞玉诏》说：从前广成子教导黄帝炼制外丹，方术中才有铅和汞这些物质，这是以人体内部修炼为法则来效法的。人刚出生时，先生成肾脏，肾属于北方的壬癸水，在五金中对应铅。接着生成心脏，心属于南方的丙丁火，在八石中对应朱砂。从铅中提取银，就像肾气中暗藏着真一之水；从朱砂中提取汞，就像心气中暗藏着正阳之气。大概是用外面的铅中之银与朱砂中之汞相合，自然结成砂状物，火候适宜，锻炼成大宝。取象类比于人，就是从肾气中取得真一之水，从心液中取得正阳之气。这两种物质结合成为丹药，就像外在事物显现出宝物一样。
《传道集》说：具备天一之质而成为五金之首的，是黑铅。铅能生出银，铅是银的母亲。感应太阳之气而成为众石之主的，是朱砂。朱砂能生出汞，汞是朱砂的儿子。难以获取的是铅中的银，容易丧失的是朱砂中的汞。铅和汞如果相互结合，经过锻炼自然成为宝物。这是铅汞的道理在外部（外丹）的表现。如果从内部（内丹）来说，父母的真气结合为一，即精血形成胞胎，凝结成为内肾。内肾就是铅。等到肾中产生气，气中生出水，用肾水与心液之上的正阳之气相结合，凝结于黄庭部位而成为丹药，这就叫真铅。将肾气与心气结合，积聚气产生液，结为玄珠，方才回归下丹田而称为汞。等到丹药炼成，真气上升，肾气进入头顶而真水下降，一升一沉，在十二楼前达成既济的状态。既济一次后回归下丹田，所以称为真汞。
《元皇君诀》说：铅汞在鼎中居住，烧炼成无价的珍珠。总共只有两个字，却读懂了万家书籍。正一真人说：铅汞传承已有几万秋，有几人领悟？有几人修行？如果让普通人懂得这个道理，尘世间的仙人就像流水一样多。吕公说：金丹一粒决定长生，必须得到真铅来炼化甲庚。火要取南方的赤凤髓，水要寻求北海的黑龟精。古今上的圣人，称说铅汞的道理各不相同，其根本只在于铅代表肾水而真铅作为丹药，汞代表心液而真汞作为药物。真铅和真汞构成既济卦象，如果凭借外丹的说法，就不能合乎道理了。
The *Xuan Dong Yu Zhao* states: In the past, Guangchengzi taught the Yellow Emperor to refine external elixirs (Waidan), and thus substances such as lead (Qian) and mercury (Gong) appeared in the formulas. This was done by taking internal alchemy (Neidan) as the standard for emulation. When a person is first born, the Kidney (Shen) forms first. The Kidney belongs to the Water of Ren and Gui in the North, corresponding to Lead (Qian) among the Five Metals (Wu Jin). Next, the Heart (Xin) forms. The Heart belongs to the Fire of Bing and Ding in the South, corresponding to Cinnabar (Sha) among the Eight Stones (Ba Shi). Extracting silver from lead is like the True One Water (Zhenyi Zhi Shui) hidden within Kidney Qi. Extracting mercury from cinnabar is like the True Yang Qi (Zhengyang Zhi Qi) hidden within Heart Qi. Generally, combining the silver within external lead with the mercury within cinnabar naturally forms cinnabar-like matter; with appropriate fire timing (Huo Hou), it is refined into the Great Treasure (Da Bao). Analogizing to humans, one extracts the True One Water from Kidney Qi and the True Yang Qi from Heart fluid. These two substances combine to form the Elixir (Dan), similar to how external objects reveal treasures.
The *Chuandao Ji* states: Possessing the quality of Heavenly One and being the head of the Five Metals is Black Lead (Hei Qian). Lead generates silver; lead is the mother of silver. Sensing the Qi of the Sun and being the master of all stones is Cinnabar (Zhusha). Cinnabar generates mercury; mercury is the son of cinnabar. What is difficult to obtain is the silver within the lead; what is easy to lose is the mercury within the cinnabar. If lead and mercury combine, refinement naturally yields treasure. This is the principle of lead and mercury manifested externally. Speaking internally, when the true Qi of parents combines into one, essence and blood form the conception sac, condensing into the Inner Kidney (Nei Shen). The Inner Kidney is Lead. When Qi arises in the Kidney, water arises from Qi. Combining Kidney Water with the True Yang Qi above Heart fluid, and condensing it in the Huangting (Yellow Court), forms the Elixir. This is called True Lead (Zhen Qian). Combining Kidney Qi with Heart Qi, accumulating Qi to generate fluid, knotting into the Mysterious Pearl (Xuan Zhu), and returning to the Lower Dantian (Xia Dantian) is called Mercury (Gong). When the Elixir is accomplished, True Qi ascends, Kidney Qi enters the crown, and True Water descends. Ascending once and sinking once, they achieve Ji Ji (Hexagram 63: After Completion) before the Twelve Towers (Twelve Towers). Returning to the Lower Dantian after one cycle of Ji Ji, this is called True Mercury (Zhen Gong).
The *Yuanhuang Jun Jue* states: Lead and mercury reside in the Cauldron, burned into priceless pearls. Simply these two characters suffice to understand the books of ten thousand families. Zhengyi Zhenren says: Lead and mercury have been transmitted for tens of thousands of autumns; how many have realized them? How many have cultivated them? If ordinary people could comprehend this principle, immortals in the mortal world would be as numerous as flowing water. Lord Lü says: A single grain of Golden Elixir (Jindan) ensures longevity; one must obtain True Lead to refine Jia and Geng. Take the fire from the red phoenix marrow of the South; seek the black turtle essence from the Northern Sea. Ancient and modern sages differ in their descriptions of the principles of lead and mercury. Their origin lies only in this: Lead represents Kidney Water, while True Lead serves as the Elixir; Mercury represents Heart Fluid, while True Mercury serves as the Medicine. True Lead and True Mercury constitute the state of Ji Ji. Relying on external explanations cannot align with the correct principles.