When a man becomes old, he often becomes pensive as well. He spends long days thinking back on his past. Back, back, back, back, back, back. Back, back, back, back, back, back, back, back, back, back, back.
The koan: "Eating the Blame"
Circumstances arose one day which delayed preparation of the dinner of a Soto Zen master, Fugai, and his followers. In haste the cook went to the garden with his curved knife and cut off the tops of green vegetables, chopped them together, and made soup, unaware that in his haste he had included a part of a snake in the vegetables.
The followers of Fugai thought they had never tasted such great soup. But when the master himself found the snake's head in his bowl, he summoned the cook. "What is this?" he demanded, holding up the head of the snake.
"Oh, thank you, master," replied the cook, taking the morsel and eating it quickly.
The enlightenment: "What is it, though?" the master repeated.
"It's the head of a snake," clarified the cook.
"Oh, okay," said the master.
This has been "Zen Koans Explained." The depth of a post hole.