both found on Mt. Kunlun. The first context describes how Yu the Great controlled the Great Flood and "excavated the wastelands of Kunlun [昆侖之球] to make level ground". "Atop the heights of Kunlun are treelike cereal plants [木禾] thirty-five feet tall. Growing to the west of these are pearl trees [珠樹], jade trees [玉樹], carnelian trees [琁樹], and no-death trees [不死樹]. To the east are found sand-plum trees [沙棠] and malachite trees [琅玕]. To the south are crimson trees [絳樹]. To the north are bi jade trees [碧樹] and yao jade trees [瑤樹]." (4.3), translating with Schafer's "malachite" instead of "coral"). The second context paraphrases the Erya definition (above) of langgan: "The beautiful things of the northwest are the qiu, lin, and langgan jades [球琳琅玕] of the Kunlun Mountains [昆侖]" (4.7), noting that qiu, lin, and langgan are "types of jade, mostly not identifiable with certainty". Medicine Several early classics of traditional Chinese medicine mention langgan. The c. 1st century BCE Huangdi Neijings Suwen 素問 "Basic Questions" section uses langgan beads to describe a healthy pulse. "When man is serene and healthy the pulse of the heart flows and connects, just as pearls are joined together or like a string of red jade [如循琅玕]—then one can speak of a healthy heart". The c. 2nd century CE Nan Jing explains this langgan bead simile: "[If the qi in] the vessels comes tied together like rings, or as if they were following [in their movement a chain of] lang gan stones [如循琅玕], that implies a normal state." Commentaries elaborate that langgan stones "resemble pearls" and their movement is like a "string of jade- or pearl-like beads". The c. 3rd century CE Shennong Bencaojing lists qīng lánggān 青琅玕 "blue-green langgan" or shízhū 石珠 (lit. "rock pearl") as a mineral drug used to treat ailments such as itchy skin, carbuncle, and ALS. This is one of the rare early references to langgan that treats it as a real substance, while many others make it a feature of the divine world. Alchemy The langgan huadan 琅玕華丹 "Elixir Efflorescence of Langgan" name of the waidan "external alchemy" elixir of immortality is the best-known usage of the word langgan. Some other translations are "Elixir of Langgan Efflorescence", "Lang-Kan (Gem) Radiant Elixir", and "Elixir Flower of Langgan". The earliest method of compounding the elixir is found in the Taiwei lingshu ziwen langgan huadan shenzhen shangjing 太微靈書紫文琅玕華丹神真上經 "Supreme Scripture