What was hidden in a sealed cave at Dunhuang for about 900 years?

A walled-up cave full of manuscripts: an estimated 50,000 documents. It was found at Dunhuang, an oasis at a religious and cultural crossroads on the Silk Road, in the Mogao Caves, a system of 500 temples. The cave, number 17, had been walled up in the 11th century and was discovered in 1900 by Wang Yuanlu, a Taoist abbot who had appointed himself guardian of some of the temples. While clearing sand on 25 June 1900, he followed the drift of smoke from a cigarette and found a walled-up area behind which was a small cave stuffed with an enormous hoard of manuscripts.

The documents date from 406 to 1002. Most are in Chinese, but many are in Tibetan, Uighur, Sanskrit, Avestan, Sogdian and Khotanese. The great majority are Buddhist, but the hoard also includes Christian Jingjiao documents, a Go manual, ancient music scores and a Chinese astronomical map.

Among them was a Diamond Sutra dated to 11 May 868, broadly considered the oldest extant printed book; earlier printed materials exist, but it is the earliest that bears an actual date. Its colophon, the note at the end, says it was reverently made for universal free distribution by Wang Jie on behalf of his two parents. A family gift, printed on a scroll, survived because a cave was sealed.

Wang later funded his restoration work by selling many manuscripts to Western and Japanese explorers, among them Aurel Stein and Paul Pelliot. The contents were dispersed around the world, and the largest collections are now in Beijing, London, Paris and Berlin. Some scholars have since described the removal as "plunder", and the Chinese government has called for the manuscripts' return.