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Various pharmacopoeias only explain the term "ash" (Hui, plant ash) but fail to explain "winter" (Dong), which is their omission. Most ashes are produced by a single roasting process, whereas winter ash requires three or four months of continuous burning in the furnace. Since the ash is subjected to fire's scorching heat day and night, how can its potency not become extremely drying and acrid? Furthermore, its physical body becomes heavier. Ashes produced in a single firing are lighter in texture, likely due to insufficient fire power, thus lacking the efficacy of winter ash. For instance, in ancient recipes such as the "Shao Rong Fang" for making tight dough, using nine-times roasted motherwort ash (Yimucao Hui) seems to adopt this principle of deep roasting. If mulberry ash (Sang Hui) is used in other prescriptions, one should naturally follow the original method. However, if winter ash is specified, it must be prepared as described above. The commentary in the *Xinxiu Bencao* (Tang Bencao) states: "Winter ash is originally made from burning chenopodium (Li grass); it is unknown if there are other explanations." Additionally, for burns and scalds, fine ash from a cake-baking furnace can be sifted through a fine mesh, mixed with sesame oil (Zhimayou), applied with a feather brush, avoiding water contact, and keeping the area away from wind.

To treat menorrhagia (blood leakage) in women, use 1 liang of silkworm sand (Can Sha), 0.5 liang of stir-fried Fulonggan (Dragon's House Liver, i.e., sediment from clay cooking stoves), and 1 liang of Ejiao (Donkey-hide gelatin). Grind them together into a fine powder. Take 2-3 qian with warm wine on an empty stomach, adjusting the dosage until the desired effect is achieved. This entry also mentions Dongbitu (East Wall Soil). Chen Zangqi stated that east wall soil is chosen because it dries out over a long period. Upon closer examination: south wall soil is also sun-exposed and dries thoroughly; why not choose it? It is likely because the east wall receives the morning sun's heating first. The Sun is the true fire of Taiyang (Greater Yang), hence it treats epidemic fevers (Wen) and malaria (Nue). One might ask: Why not choose south wall soil at noon when the sun is strongest, but instead choose east wall soil at sunrise? This is because when fire energy is generating, its qi is vigorous. Thus, the *Suwen* states: "The qi of mild fire is vigorous." By noon, the qi of excessive fire declines, so it is not chosen; this practice actually applies this principle. Another question arises: How do we know the Sun is true fire? By using a crystal lens or a concave bronze mirror to focus sunlight onto mugwort (Ai) placed at the focal point, causing fire to ignite, thereby confirming this knowledge.

Bantianhe Shui (Halfway River Water) is essentially just water. However, the rationale for using different types of water varies, each having its own theoretical basis. Bantianhe Shui, being located high up, belongs to heavenly dew/rainwater. Therefore, it is used to treat Heart diseases, Guizhu (ghostly affections/chronic wasting diseases), mania (Kuang), pathogenic evil qi, and malignant toxins. Laxue Shui (Snow Water collected in the twelfth lunar month) is extremely cold water; thus, it resolves various toxins and treats epidemic seasonal diseases (Tianxing Shiqi), warm epidemics (Wenyi), heat-type epilepsy (Re Xian), flare-ups caused by Danchi (mineral pills), sudden post-alcohol heat, and jaundice (Dan Huang). Jinghua Shui (Well water drawn at dawn) is clear, cold, and transparent water; therefore, it unblocks the nine orifices, washes away ocular and cutaneous opacities (Yi), and treats heat-dysentery following alcohol consumption. Later generations also used Dongliushui (East-flowing water), taking advantage of its swift and smooth flow to open blockages and descend stagnation in the diaphragm. Daoliushui (Backward-flowing water) is used for its swirling and stagnant nature, moving upward rather than downward.