From Kladderadatsch, 1938.  For the secret of why to roll blank dice, see Astragalomancy: A Loaded Guide: Intriguing Readings of 21 Discrete Dice Throws.  By the way, in his novel Bury Me Among the Graves, Tim Powers describes organized dice rolling without looking at the numbers: "The old dwarf tossed the objects to the floor, and Crawford saw that they were dice. McKee turned and caught Crawford's chin in her hand. 'Don't look at the numbers on them,' she said. 'But if you want to be helpful, you could pick them up and throw them, over and over again. Not looking, remember.' ... As he dropped the dice one more time onto the floor, it occurred to Crawford that he had been hearing this repetitive rattle ever since they had entered this chamber. Were these dice thrown perpetually, their numbers never read? Chuchuwee must employ a relay of children to keep it up."