The earliest artistic depiction of what might be a hand cannon – a rock sculpture found among the Dazu Rock Carvings – is dated to 1128, much earlier than any recorded or precisely dated archaeological samples, so it is possible that the concept of a cannon-like firearm has existed since the 12th century. This has been challenged by others such as Liu Xu, Cheng Dong, and Benjamin Avichai Katz Sinvany. According to Liu, the weight of the cannon would have been too much for one person to hold, especially with just one arm, and points out that fire lances were being used a decade later at the Siege of De'an. Cheng Dong believes that the figure depicted is actually a wind spirit letting air out of a bag rather than a cannon emitting a blast. Stephen Haw also considered the possibility that the item in question was a bag of air but concludes that it is a cannon because it was grouped with other weapon wielding sculptures. Sinvany believes in the wind bag interpretation and that the cannonball indentation was added later on.