Very interesting article. Readers might like to know that the image of the "Rainbow Bridge" depicted is from a later copy painting that shows a masonry bridge. This painting is in the Palace Museum collection in Taibei www.npm.gov.tw/en/Article.aspx?sNo=04007005

The authoritative Zhang Zeduan painting was "discovered" in Beijing in the early 1950s and is now readily available online showing the complex interdigitated log system under that supports the bridge upload.wikimedia.org/[...] en.wikipedia.org/[...]