The canon is seen partly as Emperor Yongle's way of declaring the legitimacy of his reign because he was controversial as a usurper. [Photo provided to China Daily]

However, the proposal was denied because, it was said, archaeological and preservation technology of the time could not guarantee appropriate conservation of imperial mausoleums, and exploratory work was stopped.

In addition, some experts say the Yongling tomb is waterlogged, so even if the canon were there it may not have survived.

Other speculation has it that the canon was burned in a fire in the imperial palace at some time or other.

Although few volumes of the canon remain, it continues to inspire many of those looking into Chinese classical documents.

According to a China Central Television documentary, the way the canon was arranged has formed the framework of a digitization project for Chinese classical documents Luan leads that started more than 30 years ago.

Whether the canon is intact or not, the way the canon is arranged is important, Luan says in the documentary.