three barriers; three passes
① Three loci in the back of the body. They are said to be hard to overcome during the first half of the Lesser Celestial Circuit (xiao zhoutian) and require for this purpose the use of three metaphoric “chariots” (sanche). Correspond to the three Cinnabar Fields placed in the front of the body.
⊛ What are the Three Barriers in the back? The one behind the brain is called Barrier of the Jade Pillow (yuzhen). The one in the Spinal Handle (jiaji) is called Barrier of the Pulley (lulu). The one at the junction of Water and Fire is called Barrier of the Caudal Funnel (weilü). (Xiao Tingzhi, Questions and Answers on the Golden Elixir, trans. in Taoist Internal Alchemy: An Anthology of Neidan Texts, p. 146)
② The three main stages in the Nanzong (Southern Lineage) codification of the Neidan practice.
⊛ What are the Three Barriers? . . . Refining the Essence to transmute it into Breath (lianjing huaqi) is the initial Barrier. Refining the Breath to transmute it into Spirit (lianqi huashen) is the middle Barrier. Refining the Spirit to return to Emptiness (lianshen huanxu) is the upper Barrier. (Li Daochun, The Harmony of the Center: An Anthology, chap. 3)