Hekiganroku - Case 18: The National Teacher's Gravestone

Emperor Shukuso [1] asked Chu, the national teacher,
  "What would you wish me to do after a hundred years ?" [2]
The national teacher said,
  "Make a seamless gravestone [3] for this old monk." 
The emperor said,
  "I should like to ask you, master, for a design."
The national teacher remained silent for a long time. Then he said,
  "Did you understand?"
The emperor said,
  "I didn't understand anything."
The national teacher said, 
  "I have a Dharma successor, my disciple Tangen, who is well versed with
   this matter. Let him come to you and ask him about it."

After the national teacher passed away, the emperor called Tangen and asked
him about the meaning of this. Tangen responded:
  "The south of the river, north of the lake:
      (Setcho commented, "The single hand does not sound without reason.")
  In between there's gold, which fills the whole land.
      (Setcho commented, "A staff, hewn freshly from the mountain forest.")
  Under the shadowless tree all people are in one boat;
      (Setcho added, "The sea is peaceful, the river clear.")
  In the crystal palace there is no one who knows.
      (Setcho commented, "The speech is finished.")"


[1] historically speaking it was Emperor Daiso the oldest son and successor
    of Shukuso.
[2] after your death
[3] an egg-formed gravestone which is made out of a single piece of stone.
    It was often made for deceased monks.