Read it through once

Those are truly wonderful diamonds, whether they exist or not; and yet they are of but little importance by comparison with the one wherewith the Boer wagoner chocked his wheel on that steep grade as heretofore referred to. In Kimberley I had some conversation with the man who saw the Boer do that—an incident which had occurred twenty-seven or twenty-eight years before I had my talk with him. He assured me that that diamond's value could have been over a billion dollars, but not under it. I believed him, because he had devoted twenty-seven years to hunting for it, and was in a position to know.