MAPINGGUAN VILLAGE, China — Liu Xing Ma was sitting in his timber-frame home here when two hikers with scraggly beards appeared in his courtyard.

That was me and my French trekking guide, Jean-Yves Tollu. We were several hours into a two-and-a-half-day, 30-mile walk through the foothills that encircle Shaxi, an ancient trading town in the southwestern Chinese province of Yunnan. And one of us — me — was terribly thirsty.

Could Mr. Liu possibly spare some water?

Our plan had been to follow vestiges of a trading route that Chinese scholars and officials call the Ancient Tea-Horse Road, and some call the Tea and Horse Caravan Trail. But the journey was bound to be quixotic, and dehydrating, because the road — which the Yunnanese authorities promote as a symbol of the area’s rich cultural heritage — is as much a historical concept as a physical entity.

Trade along the Ancient Tea-Horse Road, a title used for a informal network of caravan routes across a vast swath of Asia, began in earnest around the seventh century and peaked between the late 1600s and mid-20th century, according to Gary Sigley, a professor of Asian studies at the University of Western Australia who studies the intersection of history, tourism and politics in China. He said that on horseback, it would take about six months to travel the Chinese portion of the trail network, which began in the tea plantations of southern Yunnan and ended in Tibet.