Pu-erh tea

„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.“

„The best test is if, when drinking tea, there are any of prickling, tingling, numbing sensations on or near the tip of the tongue. If this is so one can be reasonably certain that agro-chemicals are present.“