Some references to ancient catenaries (cat-en-aries = cats eaten by canaries? a cat crossed with a canary?): http://schillerinstitute.org/educ/pedagogy/2013/vereycken-dome-1.html The Secrets of the Florentine Dome, by Karel Vereycken, 2013 http://www.naturalhomes.org/catenary.htm Obos and Beehive homes are built using Nature's Arch... The Catenary http://www.minoanatlantis.com/Minoan_Catenary_Architecture.php The Minoan Invention of the True Dome and Arch: Prehistoric Mediterranean Catenary Architecture W. Sheppard Baird December 11, 2012 "Therefore the optimal design of any arch should be one derived from a catenary form. This is exactly what was done with the Canaanite Fortification gate in the Mediterranean seaport of Ashkelon on the Levantine coast in the 19th or 20th century BC."