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Thesis
Read through modern tea science, “承一曰台一曰砧以石为之不然以槐桑木半埋地中遣” is not a lab result but a set of variables: cultivar, soil, light and plucking standard.
Text
“The cheng base, also called tai or zhen, is made of stone; otherwise of locust or mulberry wood, half-buried in the ground so that it will not rock.”
Context
承：垫在规下的台座，又叫台、砧（zhēn）。用石制；或以槐木、桑木半埋入地，使其稳固不摇。
Evidence
- Collation: 各本一致。吴觉农注："半埋地中"是为压实茶饼时台座稳固，唐代制茶作坊的朴拙智慧。
- Existing readings: 吴觉农指出"承"是压制茶饼的操作台，须稳如磐石；"槐、桑木"皆坚重之材，半埋入地以取稳——制茶之讲究，连台座也不放过。
Analysis
Modern tea science would split “承一曰台一曰砧以石为之不然以槐桑木半埋地中遣” into cultivar, soil, light and plucking variables. 吴觉农指出"承"是压制茶饼的操作台，须稳如磐石；"槐、桑木"皆坚重之材，半埋入地以取稳——制茶之讲究，连台座也不放过。 They remain testable, but only with their conditions attached.
Conclusion
The section does not give a universal rule. It demonstrates a method: read the text, the annotation and the Tang context together before making a modern claim.
Source: The Classic of Tea, Chapter II · The Implements, section 6; the original is in the public domain.
Experience should be explained, not mystified.