The Joining of Sun and Moon

Between the month's last day and dawn on next month's first day, Zhen ☳ comes to receive the token. At that moment, Heaven and Earth merge their essences, and the Sun and the Moon reach out for one another and hold onto one another.

The masculine Yang spreads his mysterious emanation,
the feminine Yin transforms her yellow wrap.
In indistinction they conjoin;
at this incipient time, the root is planted.

Steadily and orderly the seed is nourished;
from the coagulation of Spirit the corporeal frame is formed.
This is how living beings come forth:
even the wriggling worms all proceed from this.

Source: Cantong qi (Seal of the Unity of the Three), poem 10.