The image of the trigram is the mountain, heaven and earth's youngest son. The masculine is above, where by its nature it strives to go, and the feminine below, where the direction of its movement leads. So there is rest, since the movement has reached its normal end.
Applied to human beings, it shows the problem of attaining a heart at rest. The heart is very hard to bring to rest. While Buddhism seeks rest through the dying away of all movement in nirvana, the standpoint of the Book of Changes is that rest is only a polar state, which always has movement as its complement.
Perhaps the words of the text contain instructions for yoga practice.