Last week, I posted a Dogen verse here about turning the light around - an essential instruction for zazen across Zen lineages and across time.
Below you'll find another such reference by Letan Hongying (1012-1070), Linji Lineage, Huanglong Branch, nineteenth generation in China, forty-eighth since Buddha.
His phrase, "story upon story of the tower," is not a common reference. It may refer to the crystal palace of Manjushri that appears in the Flower Ornament Scripture where everything reflects everything else, especially given Letan's further reference to the "oceanic reflection samadhi."
But maybe not.
Here it is (another selection from Dahui's Shobogenzo):
Master Letan Ying said, “Zen worthies, if you can turn the light around for a moment and reverse your attention, critically examining your own standpoint, it may be said the gate will open wide, story upon story of the tower will appear manifest throughout the ten directions, and the oceanic congregations will become equally visible.
"Then the ordinary and the holy, the wise and the foolish, the mountains, rivers, and earth, will all be stamped with the seal of the oceanic reflection samadhi, with no leakage whatsoever."