"Atop Mount Wutai, the clouds are making steamed rice; below the steps of the dharma hall, a dog pisses in the direction of heaven. At the top of the flagpole, dumplings are cooking; three monkeys are sorting coins in the night."
Dogen then remarks:
If you can look at this and clearly understand it, you are like the black dragon with the pearl who can create clouds and rain wherever it goes. Otherwise, if it is not like this, you are still delighted by the lotus in the cold of December. Study this.
Now this is completely mystifying to those of us still delighted by the lotus in the cold of December.
It may or may not help much to know that Chinese dragons, the great dragons anyway, had custody of wisdom itself in the form of a pearl in their throats or under their chins. Black dragons were less auspicious than others, and were associated with difficulty, cold, the north, and deep water. The lotus is a symbol of the Buddha and his awakening; he is always depicted, when seated, on a lotus throne. And guessing, I'd say that a lotus in December, in Japan at least (and Eihei Dogen had founded a temple in a rather snowy part of Japan) is in danger of freezing.
Dogen seems to be saying, if nothing else, that admiring wisdom doesn't make you wise. That's not very goddamn helpful, which is typical of Zen. If December in Japan means it is late in the game, then we might have a reference to the historical Buddha's last words, which can be paraphrased as "life is short, seek salvation with diligence."
The steamed rice and the monkeys sorting coins and the dog lifting his leg on the temple steps may be referential of some folktales known to Chinese monks but not to us, but I suspect any such tales, if they existed, are a false clue.
Dogen is one of the great teachers of the Soto Zen tradition. In Soto Zen, you sit facing a wall. I am about to go do that. While sitting facing the wall, you are not supposed to think of Dogen's dharma talks, or dragons, or an elephant, or solutions to koans, or what you are going to do tomorrow, but one does think of one or more of those things, and the recommended course is that you recursively follow that down to a bitter end, or an ecstatic one, or else you fall asleep. Falling asleep is a failing. Or, alternatively, when you think of a dragon you just let it go, but that's very hard to do.