By constraint on the heart—one gains knowledge of the nature of consciousness.
In this verse, the heart alluded to is not the physical organ, that rhythmic biological pump that keeps the inner circulation going and hence the ‘tick tocking’ of individual existence but the centre of one’s being as the Heart Chakra.
Man is the measure of all things in the sense that he is a conscious self-aware being that has an inner as well as an outer point of reference and the dynamism between those two reference points is what is known as life. The centre of where this occurs is where they meet energetically in our subtle body (the interface) and the centre of that interface is known and designated as the Heart Chakra– ‘As above, so below’, ‘as within, so without’.
Close your eyes. Relax your body. Take a few conscious deep breaths letting go of any physical or mental stress with each out breaths.
In a detached manner (without justification or judgement) watch your mind. Witness its contents as thoughts, images, memory impressions reflect on the movie screen of awareness.
As the contents of your mind lessen and the gap between impressions increase, sink to your very centre by surrendering to those gaps.
In that centre is where Perfect Profound Peace can be experienced, the very heart of consciousness itself.