Is it not odd Sean...what we do now with "line layout" in achieving "truing" the ends of timbers and/or joint locations, with our huge 300 mm and 400 mm power planners...the Xia dynasty was doing the exact same thing (of course with hand tools..:)..) over 4000 years ago.

It's strange how systems develop from one culture to another. In some, they stayed intact in some timber framing cultures while others go off on different tangents and concepts. Since "edge rule" is a relatively modern concept (~250 years old) beginning sometime in the late 1700's with the "industrial revolution," and what we would call the "modern milling praxis"...this method took hold and held on into today's North American timber framing methodologies of layout...Even though "scribe rule" (the oldest method) and "line rule" (the next oldest) holds such superior approach to the craft. It all speaks to the strength of "normative culture and practice" often outweighing...logic, or a "better way" for lack of better words...