He was kept in prison for three years.

"My dungeon," he wrote, "is lighted by the will-o'-the-wisp alone; no breath of spring cheers the murky solitude in which I dwell.

Exposed to mist and dew, I had many times thought to die; and yet, through the seasons of two revolving years, disease hovered around me in vain.

The dank, unhealthy soil to me became Paradise itself.

For there was that within me which misfortune could not steal away; and so I remained firm, gazing at the white clouds floating over my head, and bearing in my heart a sorrow boundless as the sky." At length he was summoned into the presence of Kublai Khan, who said to him, "What is it you want ?" "By the grace of the Sung Emperor," he replied, "I became His Majesty's Minister.