1. Someone dips a rope in flammable oil before lighting it, and sees that it's quite flammable. 2. Some other time, someone tries to use a rope dipped in flammable oil as a fuse to trigger the lighting of the oil once it burns back to the oil 3. They notice that the fuse keeps burning but doesn't burn back - in other words, the wicking effect 4. They shorten the rope and reshape the pot, and that's an oil lamp.