Lower dan tian (下丹田)
Xià dāntián — qihai region
Lower dan tian (下丹田) — the storage centre of jing (essence), located in the lower abdomen approximately three cun (a body-relative measure ~ four finger-widths) below the navel, in the region of the CV6 acupoint (qihai, 'sea of qi'). In Neidan it is the foundational reservoir from which the alchemical work begins; the first transformation of internal alchemy is jing → qi, accomplished by gathering scattered essence into this centre. The coordinate corresponds to the project's LOWER_DANTIAN landmark, calibrated against the WHO Standard Acupuncture Point Locations.
Point 1 of 3 in Three Dan Tian (丹田)
Cross-tradition overlaps
No overlapping points are registered for this point.
Sources
Wei Boyang, Cantong Qi (primary_canonical)
Cantong Qi, the sections on Qian and Kun and on the tripod and vessel (Pregadio 2011), supplies the furnace-and-vessel cosmology later used to interpret the lower centre as an alchemical receptacle for refining essence; it does not fix the modern CV6 coordinate.
Zhang Boduan, Wuzhen Pian (primary_canonical)
Wuzhen Pian, the opening poems and verses on the medicine and the cauldron (Pregadio 2009), describes gathering and refining essence into qi; this supports the lower centre’s alchemical function, not a fixed anatomical CV6 location.