The king, delighted with the gift, called for his ledger; against the name of the stallion's donor he planned to write "300 riyals" -- a sum vastly exceeding the animal's value.
As he was writing, however, the tip of his pen sputtered a shower of tiny ink blots across the page, turning "300" riyals into "300,000" (the Arabic sign for zero being a dot, rather than an open '0').
"I see that my pen has decreed 300,000," the king remarked, turning to his vizier. "That is what you must pay. My hand wrote it, and it cannot be said that my hand is more generous than my heart."