There used to be an alphabetic online reference library listing of ancient metric units published by one of the local universities near me at UNC Chapel Hill NC, whose author's name I now forget being so long ago, who failed to list the remen unit in his publication. I had to take issue enough to contact him for his oversight, However I don't think he ever updated it, or that online reference library still exists now either. The internet used to be a lot more interesting experience than it is now :) John Michell certainly held it in high regard and referenced it in one of his earliest publication graphically demonstrating it's sq.rt 2 relationship to the Royal Cubit. However, as to which unit came 1st. and for what objective, I have no way of knowing for certain. It's use in area measurement work would be very handy in right triangle trigonomic calculations. That being said, I would have to go with it being of secondary origin to the RC, which by all ancient definitions was constructed from lesser units such as the Egyptian Ft., common 1.5 cubit extension, and septenary 7th. palm addendum to Royal. But all of these earlier units show a remarkable relationship to other known metrologic branches and especially to what is now called the English Metric Ft. and it's multiples and divisions. Stecchini noted in his Metrum presentation that the field of ancient metric research was divided into 2 camps, one that regarded the use of linear units being firmly connected to volumetric and weight units, and those that considered them separate in origin and evolution. Few there are these days who take on the task of evaluation of units based on the 1st. camp anymore. But that is where I find things more interesting and wouldn't have discovered Mic Saunder's value of 1,575,000,000 English Ins. Meridian Circ. otherwise. This value can be calculated from so many different angles it seems. Even though he regarded it as an approximation to his more cherished ancient Polar Pyramid Inch notion LOL! And even though I make a lot of references to this value as the more likely ancient Metric system of units counterpart to the Modern Meter, I really don't think it was ever meant as today's system equivalent. A more likely unit would be half of this measure in ratio to the RC of 20.625 ins. x 21/22 = 19.6875 ins. or 500 mm. The reason for believing this to be the more applicable is that the numerics of both of these calculations have corresponding grain weight totals also. I could elaborate more on this but that is enough said for now.