Shoyoroku - Case 17: Hogen's "Hairsbreadth"

Hogen asked Shuzanshu,
  "'If there is only a hairsbreadth of difference, it is the distance between
   heaven and earth.'[1] How do you understand that?"
Shuzanshu said,
  "If there is only a hairsbreadth of difference, it is the distance between
   heaven and earth."
Hogen said,
  "If that's your understanding, how could you ever attain IT?"
Shuzanshu said,
  "My view is just that. How about you, Master?"
Hogen said,
  "If there only is a hairsbreadth of difference, it is the distance between
   heaven and earth."
Shuzanshu made a deep bow.

[1]: Cited from the Shinjinmei (A Hymn of Sincere Mind), a work by the Third
     Patriarch Sosan. See also Miscellaneous Koans 21-2.