10 Insane Things You Never Knew About Vikings
Vikings were known to collect a type of fungus known as touchwood, which came from tree bark. Upon collecting this fungus, the society would boil it in urine for several days. The substance was then smoothed out into felt and used to start fires.
Vikings would often boil various items in urine to use for their fires, as the sodium nitrate within human urine would cause the felt from their fungus collecting to smolder instead of burn outright.