XXX: There is some "popular" way. You take a wooden line length of 20 cm, the ring (better engagement, but you can and just without a stone) hang on the thread. The option instead of a ring is a needle on a thread. You put the line on the left hand (front arm), turned with your palm up. 0 cm at the elbow, 20 cm at the palm. With your right hand over it you begin to slowly lead the thread with the ring (nail) from zero. Where it starts to bounce strongly across the line – look at the figure, it’s the "lower" pressure, and go on, it’s pumped again – here’s the "upper" pressure. The figures on the line correspond to the indications of the tonometer: 5 cm - 50, 9 cm - 90, 12 - 120, etc.
YYY: I first thought of a member enlargement benefit)))