Pour five kilograms of castor oil, one kilogram of pure white sesame oil, three ounces of veratrum nigrum, two ounces of Gleditsia sinensis, two ounces of prepared aconite root, two ounces of dried ginger, five ounces of ash, two ounces of peach kernel and one ounce of soil seed (all of which can be bought in Chinese medicine shops) into a porcelain container (iron is forbidden) and boil for four hours, then simmer with slow fire for three days and three nights, and filter out the residue. It's cold for more than ten days, then take out the jar and air it, three days in summer and six days in winter. When the remaining water vapor disappears completely, it can be used for later use. If the calcined oil can't be used up for a while, seal the jar mouth tightly and take it at any time. As long as it is well preserved and free from dust, it can be used for one hundred years.