Simply place an incense cone at the top of the waterfall and with the cone's special properties, the smoke starts to flow in reverse direction, that is from top to bottom and in-turn creates a beautiful Smokey waterfall.Back-flow incense burner creates an illusion of a smokey waterfall. Simply place an incense cone at the top of the waterfall, and with the cone's special properties, the smoke starts to flow in reverse direction, that is from top to bottom, and in-turn creates a beautiful smokey waterfall.