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Yu Yuliang (Halloysitum Rubrum): Sweet in taste, cold in nature, non-toxic. Meridian tropism is not recorded. It primarily treats cough with reverse flow of Qi, alternating chills and fever, irritability and fullness, metrorrhagia (uterine bleeding), amenorrhea, and abdominal masses (zheng jia). It also addresses joint pain, numbness of the four limbs, and severe hemorrhoids. Mu Dan Pi (Cortex Moutan) and Du Zhong (Cortex Eucommiae) serve as guiding herbs. It is incompatible with Bei Mu (Fritillariae Bulbus) and Chang Pu (Acori Tatarinowii Rhizoma), and fears ironware.

Note: Yu Yuliang derives its name from the legend that Emperor Yu collected this substance to fill his stomach when he lacked food while traveling through mountains; thus, its non-toxicity is evident. Tai Yi Yu Liang was originally the same substance, but modern practitioners often distinguish them. Chen Cangqi’s description is considered the most accurate.

Xiao Shi (Natrii Nitras): Bitter and acrid in taste, extremely cold in nature, toxic. Enters the Heart and Spleen meridians. It primarily treats accumulations in the six fu organs, dryness and urgency, retained blood and organ closure, epidemic dysentery, mania caused by Shang Han (Cold Damage), phlegm retention leading to epigastric fullness (pi syndrome), intestinal wind, and hemorrhoidal fistulas. It eliminates old pathogenic factors and generates new healthy Qi, and resolves toxicity from various mineral drugs. All types of excess heat can be purged. It can induce abortion or promote conception. Da Huang (Rhei Radix et Rhizoma) serves as a guiding herb. It is adverse to Ku Shen (Sophorae Flavescentis Radix), Ku Cai (Artemisiae Scopariae Herba), and Nu Wan (Polygalae Tenuifoliae Radix), and fears Mai Ju Jiang (Asari Radix et Rhizoma cum Terra).

Note: Xiao Shi is the essence of Tai Yin, suitable for entering the Heart meridian to drain fire. Since the Spleen is the child of the Heart, it also enters the Spleen meridian. Danxi stated: "The *Shennong Ben Cao Jing* claims it is non-toxic, which is an error! How could it dissolve seventy-two types of stones without being toxic?" There are six varieties of Xiao Shi with identical flavors and properties, all good at digestion and expulsion. However, Pu Xiao (Mirabilite) has a strong force, Mang Xiao (Glauber's Salt) and Ma Ya Xiao have a milder force, while Feng Hua Xiao (Effloresced Glauber's Salt) and Xuan Ming Fen (Refined Mirabilite) are even milder. When used for treatment, discontinue once the disease recedes. The claim in the *Ben Cao Jing* that refined use provides tonification is illogical. The classic states: "When heat dominates internally, treat with salty-cold agents, assisted by bitter-cold agents." Ancient formulas therefore commonly use Da Huang to assist Mang Xiao.

Leigong said: When preparing, first grind into powder. Place in a porcelain bottle and heat over five jin of fire until red-hot. Mix Ji Chang Cai (Purslane) and Bai Zi Ren (Biota Seed) together, form into small cake-sized pills. When the pills turn red, throw the Xiao Shi into the porcelain bottle; the Xiao Shi will naturally subdue the fire. For every four liang of Xiao Shi, use fifteen units of Ji Chang Cai and Bai Zi Zi combined, until the contents in the mortar are fully transformed.

Hua Shi (Talcum): Sweet and bland in taste, cold in nature, non-toxic. Enters the Stomach and Bladder meridians. It primarily promotes urination, consolidates the Large Intestine, transforms food toxins, moves stagnation, expels coagulated blood, relieves dry thirst, guides lactation, tonifies the Spleen and Stomach, and descends reckless fire. The white, fine-textured variety without yellow sand is superior. Gan Cao (Liquorice Root) and Shi Wei (Pyrrosiae Folium) serve as guiding herbs. Qing Hai (Azurite) is mentioned.

Note: Hua Shi is sweet, suitable for the central region (Spleen/Stomach); it is bland, suitable for promoting water metabolism, which explains its entry into the Stomach and Bladder. Although beneficial, it is ultimately a draining agent. Without Gan Cao to harmonize it, it should not be used alone.

Leigong said: There are many varieties of Hua Shi; do not use them incorrectly. There are White Hua Shi, Green Hua Shi, Black Hua Shi, Cold Hua Shi, and Yellow Hua Shi. White Hua Shi resembles Calcite, is white in color, and is identified by white fine textures on the stone surface. Green Hua Shi is cold in nature and toxic; it must not be used in medicine. Black Hua Shi appears blackish with green-white fine textures on the surface and is excellent for medicinal use. Yellow Hua Shi resembles golden round grains with green and black markings on the surface; do not use it, as it can cause death. Cold Hua Shi is bluish-green with white fine textures on the surface; do not use it. True Hua Shi resembles pale blue-white water color with fine textures on the surface. When preparing, scrape the surface with a knife, grind into powder, and boil together with Mu Dan Pi (Cortex Moutan) for one shichen (two hours). Remove the Mu Dan Pi, take the Hua Shi, wash it with flowing water from the east, and dry it in the sun before use.