The soonest realized crossbows were designed in the main thousand years BC, not later than the seventh century BC in old China, not later than the fourth century BC in Greece (as the gastraphetes).
Gunpowder was developed in China at some point during the main thousand years AD. The most punctual conceivable reference to gunpowder showed up in 142 AD during the Eastern Han administration when the chemist Wei Boyang, otherwise called the "father of speculative chemistry", expounded on a substance with black powder like properties.
