Genjo Koan

"Though there are many features in the dusty world and the world beyond conditions, you see and understand only what your eye of practice can reach. In order to learn the nature of the myriad things, you must know that although they may look round or square, the other features of oceans and mountains are infinite in variety; whole worlds are there. It is so not only around you, but also directly beneath your feet, or in a drop of water."

"The dusty world" refers to this world we live in.

"The world beyond conditions" refers to the Pure Land.

"Eye of practice" means the mind realized through mindful practice.

"The nature of myriad things" refers to Buddha Nature.

"Whole worlds" refer to the vastness of oceans and mountains.
"Ocean and mountains" refer to nirvana and samsara and its relationship to mindful practice of meditation.

This koan is encouraging the Zen practitioner to look beyond the limitations of mindful practice as determined by what one already knows.

It inspires one to use imagination to see there is more to practice than just sitting.


Reference:
Genjo Koan: http://www.thezensite.com/ZenTeachings/Dogen_Teachings/GenjoKoan8.htm