Special Report 2/23/04Marco Polo in Reverse In the spring of 1288 a curious throng packed the Vatican to celebrate Easter and glimpse a visitor from the far side of the world. Rabban Sauma, a Mongolian Christian, had braved a 7,000-mile trek from Beijing. But when he received the Eucharist from the pope, he broke down and sobbed. The crowd's loud amens shook the church. Sauma was the Mongol Empire's first envoy to Europe, just 50 years after Mongol armies were repulsed at the gates of Vienna. Much of his diaries have survived, giving a unique perspective on the West. "Sauma...