There is no definitive conclusion. Wikipedia records that the Táng Thư is a work of the 4th or 5th century and attributes it to Quách Phác (276 to 324), but this is a traditional attribution, not a conclusion verified by textual scholarship. The book Phong thủy cổ đại Trung Quốc: lý luận và thực tiễn, volume 2, also records the legend that Quách Phác received this art from a recluse, and holds that later generations may have borrowed his name to lend prestige to feng shui books.
Qi in feng shui is the invisible flow the Zangshu describes as scattering in wind and stopping at water. It covers sheng qi, si qi, cang feng, and de shui.
The Four Symbols guard the huye: Thanh Long left, Bạch Hổ right, Huyền Vũ behind, Chu Tước in front. This piece covers their shapes and the minh duong layers.
Hexagram Phong Thủy Hoán, number 59 in the I Ching, covers the Judgment, the Image and all six line texts, plus gathering people's hearts when things scatter.
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