Since I have made actual measurements, I can state that the Stonehenge curvatures are not in any conceivable sense related to Greek or Roman entasis. In fact, the uprights of Stonehenge are typically curved as the arcs of circles. And in reated research, I believe I have identified these circles as being related to halos, thus leading to the suggestion that Stonehenge was a halo observatory. The sagittometer was designed to measure the curvature of the stones of Stonehenge, the idea being to test the idea that these stones were carved with arcs of circles. This idea contrasts with the claim, made by some, that the curvature is entasis, the technique used by the Greeks for their pillars.
Entasis is supposed to make tall pillars appear parallel in outline correcting an optical illusion.
Why else would an American travel all the way to England to measure the curvature of stones. Given the theme, somewhat equivalent to a Monty Python extravaganza, placing the sagittometer in the nearby museum seemed a bit of sly British humor. Nevertheless, I did receive 15 seconds of fame trying to explain the halo idea on British television. Drawing by Annette Cyr from Stonehenge Expedition Photo.