"Find Grandpa Amu on YouTube, where he demo ancient Chinese woodworking traditions. In his most popular video he builds a Rainbow Bridge just the right size for his grandbaby."
"The documentary is from NOVA ( https://www.pbs.org/wgbh/nova/lostempires/china/builds.html ) about the design that predates da Vinci by several hundreds of years. Check out http://happypontist.blogspot.com/2018/07/chinas-unique-woven-timber-arch-bridges.html to read up on the Rainbow Bridge."