In the Shōbōgenzō chapter, Jinzu, Dogen talks about mystical powers.
At his time, many people thought that through the practice of Zazen, practitioners acquired mystical powers, such as the ability to see into past lives, to change form, and so forth.
The hope of personal enlightenment is a residue of this sort of thinking. But we need to understand that whatever can be grasped makes us a fist.
For Dogen, these mystical powers were the small mystical powers, not the great mystical power.
So what is the great mystical power?
For him, it was chopping firewood and carrying water. In other words, ordinary activity. The great miracle that there is something, not nothing.
Zenki is the great mystical power
Gratitude, love, is the great mystical power
Unclenching the fist of the mind is the great mystical power
The world and the heart leaping out of each other. The Great Mystical Power.