Stillness
By stillness I don't mean that there is no movement, physical
or mental movement. I'll explain more. When I say that there is
no stillness, I mean that when you observe any object of your
perception, you are looking at it from a place that is either
going toward or way from what you are looking at. You are either
saying, "I want it" or "I don't want it."
So the place that you are coming from is in constant movement;
it is not still. Real stillness penetrates all the way through
to the place that you are coming from, or rather, it emanates
from there. It doesn't mean that there is no movement in the field
of perception. It has nothing to do with whether the body is moving
or not. It is your center that becomes a stillness. (Diamond Heart
Book 3, pg 178)

Stillness of the mind. In order to recognize true liberation
you must have this capacity for stillness or peacefulness, because
liberation is so fleeting. If you are thinking and worrying and
planning and carrying on your normal fast-paced activities, you
are precluding this experience from your life. As you develop
and appreciate the stillness that leads to the absence of agitation,
you allow a state of restfulness that leads to intuition, to
insight, and to the subtle perceptions. (Diamond Heart Book 2)

I recognize the state as a luminous black spaciousness, which
is the unity of stillness and space. There is immaculate, glistening
emptiness, but the emptiness has a sense of depth. The depth
seems to be the felt aspect of the blackness of space. It is
like looking into, and feeling into, starless deep space. (Luminous
Night's Journey)

The darkness of the night expresses the depth, stillness,
and mystery of the black peace essence; the redness of blood
and fire reflects the vitality and vigorous energy of the red
strength essence; the yellow of the sun and of flowers embodies
the lightness and delight of the yellow joy essence, and so on.
In such experience the two levels of differentiated forms appear
as a unified gestalt, unified by the boundless presence of basic
knowledge. (Inner Journey Home)