Hi there!
As we may know, people didnt have light bulbs or electricity till at least 1879, therefore we can imagine they might have used natural sunlight, and of course fire. Fire has a lot of uses, and they might have found different ways to use it. For instance, candles. These were invented just like a flashlight, with fire. Fireplaces. Before our age we know they could only use natural resources.
Hope this helps you!
~DL