Two rare volumes of an ancient Chinese encyclopedia sold for more than 8 million euros (US$9 million) at auction Tuesday, more than 1,000 times the estimated price.

The encyclopedia, known as the Yongle Dadian, was originally commissioned by the Yongle Emperor, the third ruler of the Ming Dynasty, who reigned from 1402 to 1424.

More than 2,000 scholars worked on the encyclopedia between 1404 and 1408, according to a press release from Beaussant Lefèvre, the Paris-based auction house that made the sale.

The Yongle Dadian is the largest encyclopedia in the world, and originally consisted of 22,877 chapters.

In 1562, the Jiajing Emperor, the 11th Ming ruler, ordered two copies of the encyclopedia to be made, but the original was lost due to the many wars, thefts and fires that occurred under the Ming Dynasty (1368-1644), the auction house said.

While the two volumes sold Tuesday are copies, they are extremely rare, with only 400 known volumes, or 4 per cent of the original encyclopedia, left in existence, according to Beaussant Lefèvre.

The books, which measure 20 inches by 12 inches, were written in red and black ink on paper. While printing techniques had been developed at the time, the encyclopedia was written by hand due to its length.

One volume is about the lakes of China and the other informs readers about funeral rites. Together, they were bought by an unnamed buyer for €8.128 million including fees. Before the auction, they carried a price estimate of €5,000-€8,000.

The British Library has 24 volumes of the encyclopedia, equivalent to 49 chapters.

The Yongle Emperor was a strong leader who presided over the most powerful years of the Ming Dynasty.

In 1412, he ordered the construction of the famous Porcelain Tower in Nanjing.

The tower took 17 years to complete and was known as one of the Seven Wonders of the Medieval World.

It was built with glazed, white porcelain bricks and rose more than 250 feet from an octagonal foundation, but the original was thought to have been destroyed during the Taiping Rebellion in the 19th century.

However, a new version of the tower has been constructed following a 1 billion yuan (about US$150 million) donation from Chinese billionaire Wang Jianlin in 2010.