To make a groove in the Cullinan an enormous amount of scherp (sharp edged pieces of rough diamond to scrape away the groove) were prepared. This was a very expensive exercise, but given the task ahead, that didn’t seem to matter.
Joseph Asscher was a strong man, somewhat thickset, like Tommy Burns the then middleweight boxing champion. An hour after commencing the cleaving process both his hands were swollen. Rest? No that was not an option. A day and a half later the groove was ready. My brother Joseph thought that the special knives made by Herder were a little too long for this job, so he asked me to shorten one of them. But how on earth do you quickly shorten an hardened steel blade. Use a grinder? Heat it and saw through it and then harden it again, much too complicated.
I knew exactly what I had to do. I went to the workshop and placed the blade in a heavy vice, and with all my strength gave an almighty hit with a sledge hammer! It broke in exactly the perfect place.
(On the 10th February 1908 in the presence of both John & Alexander Levy, all of the Asscher brothers, and witnessed by Hendrik Wertheim, Notary, the Cullinan was ready to be cleaved)
Two minutes later the blade was placed in the groove, Joseph hit it with power! The stone didn’t split. The blade flew through the room. Blade broken! Was shouted. “No not at all!’ I said “that’s just where I shortened it”. I gave him another blade slightly thicker this time and said, “Give it a good old whack!” Again he hit it with enormous explosive power. “Crick” was the sound the stone made, it split into two, and both faces were as smooth as a mirror. The black inclusion was now in both pieces as intended.
Joseph drank two or three brandy and soda and grinned with satisfaction. Up to the present he is the ‘Undisputed World Champion’ in the cleaving of large rough diamonds!