This has been very popular since the 18th century, combined with a cannon and a burning glass, is set so that when the sun reaches its highest point at noon, a charge of gunpowder is ignited by the bundled rays of the sun, so that a loud bang sounds. In arsenals and dockyards large specimens were used as call signs for noonday and lunchtime.

Tfw the sun isn't out to power your gundial but your opponent won't postpone the duel :/