A potometer measures how factors such as light, temperature, humidity, light intensity and wind will affect the rate of transpiration. The main type of potometer is the 'bubble' potometer shown in Figure Figure 6.
Physicians recommended against the practice because they did not want medicines associated with punishment. A heavy dose of castor oil could be used as a humiliating punishment for adults, especially political dissenters. Colonial officials used it in the British Raj (India) to deal with recalcitrant servants. Belgian military officials prescribed heavy doses of castor oil in Belgian Congo as a punishment for being too sick to work.
In the European folk medicine, castor oil pack is applied to the painful area to reduce the pain. For the treatment you will need good quality hexane-free castor oil, cotton flannel, a plastic wrap, a bath towel and heating pad or a hot water bottle. Castor oil stains cloth. Therefore use old clothes and towels.