Ikkyu, a famous Zen teacher of Ashikaga era, was the son of the emperor. When he was very young, his mother left the palace and went to study Zen in a temple. Prince Ikkyu also became a student. When his mother passed away, she left him a letter. It read:

"To ikkyu, I have finished my work in this life and am now returning to eternity. I wish you to become a good student and to realise your Buddha-nature. You will know if I am in hell and whether I am always with you or not. If you become a man who realises that the Buddha and his follower Bodhidharma are your own servants, you may leave studying and work for humanity. If you don't and yet wish to, avoid thinking fruitlessly. Your mother, not born, not dead. September 1st. P.s.: The teaching of Buddha was mainly for the purpose of enlightening others. If you are dependent on any of its methods, you are naught but an ignorant insect. There are 80,000 books on Buddhism and if you should read all of them and still not see your own nature, you will not understand even this letter. This is my will and testament."