I always enjoy your Saxon/Indus astronomical units system evaluations. What both you and Cloister mention got me thinking about the use of "Conventions" as differing from "Convictions", regarding unit measures. As in the case of the convention that a cubic Ft. of Water weighs precisely 1000 Av/Ounces of 437.5 gr/ou. This has been cited for centuries, and it amounts to an Av/Lb. total of 62.5 Lbs. The only problem with this convention, is that it couldn't possibly weigh this amount even on a very cold winter night with pouring rainfall being collected at it's densest point just above freezing into snow or ice of 4*C, which is what the current definition of a Metric gram of Water density is based on. In addition to a few tons of coal fired chimney smoke particulate from a few hundred thousand dwellings in Ye Old Victorian city of London added to the mix, still couldn't arrive at the stated target of 62.25 Lbs per. cu/ft. This is also my perception of an Earth sphere based on an idealized Circ. dimension of 25,000 Mis. or as David cites, 132,000,000 Ft. That figure is useful as a convenient convention for many general purpose simplistic calculations, but it wasn't meant to be regarded as a realistic figure of the Earth's dimensions.
edited to change the value of a cubic Ft. of Water density from 62.25 Lbs. to the correct total of 62.5 Lbs.
Edited 1 time(s). Last edit at 03-Jan-18 13:12 by magisterchessmutt.