Are there any scriptures defining what "wholesome meditation" is with
relation to all the Skandha and not just one?
It is rather spoken of as directing of the past, present & future classes of what can be spoken of in terms of genesis, forms cognizable via five senses & mental apprehension, feelings/sensations, perception & or consciousness.
Sutta say that the final awakening to the truth is the final goal, anything conducive to it is wholesome, anything counter productive is unwholesome. That being any state of mind's development.
Particular Sutta would be those dealing with directed & undirected development, two sorts of thinking, removal of distracting thoughts, themes for frequent reflection, nourishment & denourishment of hindrances, pleasant abidings, contemplation and or the defining of the elements for perception development
"'Consciousness, consciousness': Thus is it said. To what extent,
friend, is it said to be 'consciousness'?"
"'It cognizes, it cognizes': Thus, friend, it is said to be
'consciousness.' And what does it cognize? It cognizes 'pleasant.' It
cognizes 'painful.' It cognizes 'neither painful nor pleasant.' 'It
cognizes, it cognizes': Thus it is said to be 'consciousness.'"
"Discernment & consciousness, friend: Are these qualities conjoined or
disjoined? Is it possible, having separated them one from the other,
to delineate the difference between them?"
"Discernment & consciousness are conjoined, friend, not disjoined.
It's not possible, having separated them one from the other, to
delineate the difference between them. For what one discerns, that one
cognizes. What one cognizes, that one discerns. Therefore these
qualities are conjoined, not disjoined, and it is not possible, having
separated them one from another, to delineate the difference between
them."
"Discernment & consciousness, friend: What is the difference between
these qualities that are conjoined, not disjoined?"
"Discernment & consciousness, friend: Of these qualities that are
conjoined, not disjoined, discernment is to be developed,
consciousness is to be fully comprehended."[1]
"Feeling, perception, & consciousness are conjoined, friend, not disjoined. It is not possible, having separated them one from another, to delineate the difference among them. For what one feels, that one perceives. What one perceives, that one cognizes. Therefore these qualities are conjoined, not disjoined, and it is not possible, having separated them one from another, to delineate the difference among them." - https://www.accesstoinsight.org/tipitaka/mn/mn.043.than.html
Form is the only aggregate which isn't conjoined with the others because form is the perceived object and perception can be otherwise & without form for object, having a formless object that is approached by stilling of the perception based on forms.
Another way of grasping this is that genesis/conception conceives something, perception perceives something, feeling feels something, conscioussness cognizes something; whereas form is that which is generated, cognized, felt & perceived and conception can be of something else, a mental object like perception of the infinitude of space or nothingness.
As he was sitting there, he said to Ven. Sariputta, "Friend, 'One of
poor discernment, one of poor discernment': Thus is it said. To what
extent is one said to be 'one of poor discernment'?"
"'One doesn't discern, one doesn't discern': Thus, friend, one is said
to be 'one of poor discernment.' And what doesn't one discern? One
doesn't discern, 'This is stress.' One doesn't discern, 'This is the
origination of stress.' One doesn't discern, 'This is the cessation of
stress.' One doesn't discern, 'This is the practice leading to the
cessation of stress.' 'One doesn't discern, one doesn't discern': Thus
one is said to be 'one of poor discernment.'"
"Discernment & consciousness, friend: Of these qualities that are
conjoined, not disjoined, discernment is to be developed,
consciousness is to be fully comprehended."
The eye of discernment [judgement]
"Friend, what can be known with the purified intellect-consciousness
divorced from the five [sense] faculties?"
"Friend, with the purified intellect-consciousness divorced from the
five faculties the dimension of the infinitude of space can be known
[as] 'infinite space.' The dimension of the infinitude of
consciousness can be known [as] 'infinite consciousness.' The
dimension of nothingness can be known [as] 'There is nothing.'
"With what does one know a quality that can be known?"
"One knows a quality that can be known with the eye of discernment."
"And what is the purpose of discernment?"
"The purpose of discernment is direct knowledge, its purpose is full
comprehension, its purpose is abandoning."
- First the theme of sensuality is stilled
- Then sustained entertaining of thought is stilled
- Then application of thought is stilled
- Then physical elation is stilled
- Then mental eleation is stilled
There remains only quanimity based on form, bodily feeling, sensation of the wind, sensation of the liquidity or float, or
otherwise a vision of lights & colors.
Furthermore there is a stilling of the perception of form.
There remain only the formless 'signs' where is 'form signs' are associated with perception based on material field/context of conception.
Furthermore there is a stilling of signs and analogical contact with the signless grasped as the principal stilling of perception & feeling and this attainment is grasped as signless, empty or undirected depending on how it was approched & personal inclination due to prior development.
This is sutta analysis and analysis is made explicit in the Theravadin canon (Vibhanga (abi)
