One of the earliest light sources was the fatwood, also known as fat lighter, lighter wood, rich lighter, pine knot, lighter knot, heart pine or lighter'd. It was simply a thin piece of wood which was burning on one end, the flame used as light source. The problem is, that wood burns rather fast and probably with a big flame, but the goal was to get a small flame which burns constantly and as long as possible. That's why this was made of the heartwood of pine trees, the stump and tap root in the ground after a tree has fallen or has been cut. The wood is impregnated with resin which makes it hard and rot-resistant, even when the tree is gone. The high amount of resin is what makes this a relatively good light source. It was working like a candle, the wood was the "wick", the resin was the wax.
Fatwood can not only be used as a light source, but also as a lighter for a fire. It burns easily and placed in a pile of wood it will start a fire. Many of the traditional names are deried from this use and for this use it is sold until today. It is called firestarter or ecostix, just search for fatwood on Amazon and you see what I mean. Advertised as a natural alternative to the modern fire starters which are made of petroleum.
When used as a light source, the fatwood is cut into long sticks. Then the stick is burned on one side. There are numerous kinds of holders, or the people simply put the other end in their mouth. The trick was to hold it more or less horizontally, and by changing the orientation up and down the speed of burning could be influenced. But there are so many drawbacks about using fatwood as a light source, here are only the most important: