When we think of traditional timekeeping, what often comes to mind are mechanical devices such as the watch and clock. Prior to these modern concepts, people relied on various clever methods, including: The hourglass, various astrological signs,sundials, pendulums, chronometers and even candles. Yes, Candles!
For centuries, people have used candles for various timekeeping measures. While the candle could not tell you the time of day, it was a reliable source for providing a fairly accurate interval of time.
Perhaps the most common use for the candle as a timer during ancient times was its use an alarm clock. Dating back as early as 520 A.D. the Chinese would take a pillar style candle and insert a tack or a nail into the side of the candle before going to sleep. The candle would typically have markings spaced out down the side of the candle measuring the length of burn time between markings. The tack or nail, made of metal would hold its place in the candle until the wax melted down to where it was lodged. When the wax melted, the metal piece would loosen and fall. Beneath the candle lay an empty metal dish. When the nail dropped, it would make a loud clatter sound waking up the nearby sleeper.
This method was particularly useful when sleeping in dark quarters where no sunlight shined through.
Imagine a Few What-IFs:
If we used candles as our alarm clock today, how many people would be late to work?
If every household left a candle burning nightly, how much more often would there be a house fire?