Hi Dbfirs, Thanks for providing these details. It would be most interesting if we could identify other mathematicians that used the constant 6.283... rather than 3.14159... I guess that Euler was such an important mathematician that everybody after him used pi to denote 3.14159..., but it would surprise me if David Gregory was the only one of that time to be interested in the circumference divided by the radius rather than the diameter.  EntroPeter