“All the waters return to the great ocean” : this sentence reflects an absolute truth.
Rain, streams, rivers, all waters, whatever their flavours, whatever their tastes, return to the great ocean whose taste is one, unique. All the rivers of the mind flow towards the great ocean of the mind. All forms of the mind return to the original mind. We can also say: all waters come from the great ocean, all thoughts come from the original mind.
It is this truth that we verify by ourselves in zazen. To do this, keep your posture immobile, vertical.
All waters flow towards the great ocean, the original ocean. All the water comes from the great ocean with its unique taste. If you are in accord with this reality, if you do not oppose it, the way is realised.