William Muir,
The Caliphate: Its Rise, Decline and Fall…
“ Meeting 'Omar in the marketplace, he cried out, "Commander of the Faithful! right me of my wrong, for verily Al-Moghira hath assessed me heavily." "At how much ?" asked the Caliph. "At two dirhems a day." " And what is thy trade?" "A carpenter and worker in iron," he said. "It is not much," replied 'Omar, "for a clever artificer like thee. I am told that thou couldest design for me a mill driven by the wind." "It is true." "Come then," continued the Caliph, "and make me such a mill that shall be driven by the wind." ”
