|Drawing of a Fei Kong Ji Zei Zhen Tian Lei Pao, from 'Wu Bei Zhi (《武備志》)'.|
Incidentally, this is not the first weapon to bear the name of Zhen Tian Lei (震天雷, lit. 'Skyshaker thunderbomb'). The original Zhen Tian Lei is a type of trebuchet-launched cast iron bomb developed by the Jurchen of the Jin Dynasty in their war against the Mongols.
Another version of Zhen Tian Lei, this time used by the Mongols against the Jurchen, is possibly launched from a cannon.
The Koreans of the Joseon Dynasty also had their own version of Zhen Tian Lei called bijincheonloe (비진천뢰 or 飛震天雷, lit. 'Flying skyshaker thunderbomb') or bigyeok jincheonroe (비격진천뢰 or 飛擊震天雷, lit. 'Skyshaker thunderbomb of flying attack'). It is a cast iron delay-action shell that can be launched from a bombard or mortar. This weapon can be considered an early forerunner of time bomb.
|Joseon Dynasty bijincheonroe, from 'Yungwon pilbi (《융원필비》 or 《戎垣必備》)'.|