Materials for the enema nozzle and size of its opening

The nozzle is to be made of gold, fine silver, copper, wood and the like, unbroken, with a smooth ball at its mouth; the opening inside the tip is the size of a cooked mung bean, pigeon pea and pea for children, youths and young adults respectively. A footnote on the preceding commentary explains that the collar keeps the whole nozzle from entering the anus.