Where does Camphor flavor in Puerh tea come from?

„Depending on the desired product and speed, from quickest and tightest to slowest and loosest, pressing can be done by a large heavy stone, carved into the shape of a short cylinder with a handle, simply weighs a bag of tea down onto a wooden board. The tension from the bag and the weight of the stone together give the tea its rounded and sometimes non-uniformed edge. Due to the manual labor involved, this method of pressing is often referred to as: "hand" or "stone-pressing", and is how many artisanal pu'er bǐng are still manufactured.“