The faculty of sight is potentially available on every plane and subplane, given a suitable light body and sufficient practice. Thus the subplane matter, when in sufficient quantity can, with practice, be formed into a sight organ.
While most people can visualise to some degree with the lowest subplanes of the mind, only a minority are practiced at seeing with the mind. Visualisation can be a purely internal practice while seeing with the mind may involve contact with the greater reality. The lower mental sub-planes are more subject to bubbles and hence seeing on those sub-planes is less reliable.
Seeing with the heart is rare in humans, mainly because humans tend to be focussed on the emotional sub-planes with regrettably little activity on even the lowest heart sub-plane.
The higher sub-planes of heart perception may be characterised by a systemic rather than personal viewpoint. Heart perception has a different quality of certainty - being beyond mental evaluation
A useful test for the initiate when faced with a difficult circumstance is to consider whether the pain is emotional and mental or whether there is some heart pain. As a general rule if there is no heart pain then there is no fundamental problem.
Would that be comparable to the gut feeling we discussed a while ago (in relation to the plumbline)? To me its located around (perhaps slightly below) the solar plexus..
The cross is the human body through which the divine soul goes its 'path of the cross':
From Bethlehem (the heart) to Golgotha (the mount of the skull) to his resurrection, passing through hell (the sacral plexus, the subconscious) and to the eternal Fatherland (the Father).