In Journey to the West, the monkey king, an earnest seeker after the Dao, tells us: "In yonder mountains lives an old immortal; his age is 18,000 years. I asked him to be my master, to teach me the way of longevity. He said the elixir of life is within your own body; to seek it elsewhere is a waste of effort."
《西遊記》裡，誠心訪道的老孫自我介紹：那山有個老仙長，壽年十萬八千高，老孫拜他為師父，指我長生路一條，「他說身內有丹藥，外邊採取枉徒勞」。