I once read in one of Gierach's books that AK Best had a picture of the pool that the Adam's dry fly was tested/inspired out of. Does anyone know what river/pool this was? Does anyone have a picture of this fly?

The Adam's dry fly is my go to fly for sooo many different hatches. I've caught so many fish on it, that I even feel confident casting it in MA in January

Any info on this would be great and appreciated.