The path is explained here (the very advanced stages) :
sn35.245/en/sujato
45. The Simile of the Parrot Tree
245. Kiṃsukopamasutta
1.1Then one mendicant went up to another mendicant and asked,
Atha kho aññataro bhikkhu yenaññataro bhikkhu tenupasaṅkami; upasaṅkamitvā taṃ bhikkhuṃ etadavoca:
1.2“Reverend, at what point is a mendicant’s vision well purified?”
“kittāvatā nu kho, āvuso, bhikkhuno dassanaṃ suvisuddhaṃ hotī”ti?
1.3“When a mendicant truly understands the origin and ending of the six sense fields, at that point their vision is well purified.”
“Yato kho, āvuso, bhikkhu channaṃ phassāyatanānaṃ samudayañca atthaṅgamañca yathābhūtaṃ pajānāti, ettāvatā kho, āvuso, bhikkhuno dassanaṃ suvisuddhaṃ hotī”ti.
2.1Not content with that answer, that mendicant went up to a series of other mendicants and received the following answers:
Atha kho so bhikkhu asantuṭṭho tassa bhikkhussa pañhaveyyākaraṇena, yenaññataro bhikkhu tenupasaṅkami; upasaṅkamitvā taṃ bhikkhuṃ etadavoca:
2.2
“kittāvatā nu kho, āvuso, bhikkhuno dassanaṃ suvisuddhaṃ hotī”ti?
2.3“When a mendicant truly understands the origin and ending of the five grasping aggregates, at that point their vision is well purified.”
“Yato kho, āvuso, bhikkhu pañcannaṃ upādānakkhandhānaṃ samudayañca atthaṅgamañca yathābhūtaṃ pajānāti, ettāvatā kho, āvuso, bhikkhuno dassanaṃ suvisuddhaṃ hotī”ti.
3.1
Atha kho so bhikkhu asantuṭṭho tassa bhikkhussa pañhaveyyākaraṇena, yenaññataro bhikkhu tenupasaṅkami; upasaṅkamitvā taṃ bhikkhuṃ etadavoca:
3.2
“kittāvatā nu kho, āvuso, bhikkhuno dassanaṃ suvisuddhaṃ hotī”ti?
3.3“When a mendicant truly understands the origin and ending of the four primary elements, at that point their vision is well purified.”
“Yato kho, āvuso, bhikkhu catunnaṃ mahābhūtānaṃ samudayañca atthaṅgamañca yathābhūtaṃ pajānāti, ettāvatā kho, āvuso, bhikkhuno dassanaṃ suvisuddhaṃ hotī”ti.
4.1
Atha kho so bhikkhu asantuṭṭho tassa bhikkhussa pañhaveyyākaraṇena, yenaññataro bhikkhu tenupasaṅkami; upasaṅkamitvā taṃ bhikkhuṃ etadavoca:
4.2
“kittāvatā nu kho, āvuso, bhikkhuno dassanaṃ suvisuddhaṃ hotī”ti?
4.3“When a mendicant truly understands that everything that has a beginning has an end, at that point their vision is well purified.”
“Yato kho, āvuso, bhikkhu yaṃ kiñci samudayadhammaṃ, sabbaṃ taṃ nirodhadhammanti yathābhūtaṃ pajānāti, ettāvatā kho, āvuso, bhikkhuno dassanaṃ suvisuddhaṃ hotī”ti.
In all of this effort, viriya, energy was present but without wrongview.
Also a useful quote from Nina van Gorkom:
Some people separate pariyatti from pa.tipatti which they see as something that is not part of their normal daily life, as something particular they have to be engaged in. They forget that when they study the theory, pariyatti, they should study with the aim to understand the reality that appears at this moment. One should study in order to understand that any reality of this moment is dhamma, be it seeing or hearing, but one never knew before that it was dhamma. Thus, people should study with the aim to correctly understand that naama dhamma at this moment is the reality that experiences, the element that experiences. Naama dhamma is not theory, but there is naama dhamma while we are seeing now. One may have heard and understood that seeing at this moment is naama dhamma, because it is a reality that experiences something, but the expression “the reality that experiences” is most difficult to understand and to penetrate. When one sees, there is something that is appearing through the eyes, but the reality of naama that sees does not appear. Only when its characteristic appears, it can be known as an element or a kind of dhamma that is real.
When people have understood this, they know that what is appearing through the eyes at this moment could not appear if there would not be naama dhamma that has arisen and sees that object. One can gradually understand that seeing at this moment is dhamma. Therefore, when one studies the Dhamma one studies with the purpose to have right understanding of the characteristics of realities that are the truth of each moment in daily life. This can be a condition for sati to arise and to be aware and in this way one will gradually understand that when one sees at this moment, it is a reality, an element that experiences, or when one hears, that it is an element experiencing sound.
People who listened at the time when the Sammaasambuddha had not yet finally passed away, could understand immediately the characteristics of naama and ruupa. The reason was that they had developed understanding, that they had listened and considered what they had learnt to a great extent. When we read the life stories of those people we see that, before they could realize the four noble truths at the moment of enlightenment, they had to study and listen a great deal during many lives, so that they could become bahussuta. A person who is bahussuta (bahu is much, and suta is heard) is someone who has listened and studied a great deal in order to understand realities. As Khun Nipat has said, at that time there were no books.
Therefore, people listened with understanding and they did not think of textbooks or different subjects written down in books. They heard about realities that were appearing, they could investigate and understand them immediately. Their study was based on listening and considering, they knew that what they heard concerned the reality appearing at that very moment.
When the Buddha asked whether seeing was permanent or impermanent, they answered, “impermanent”. They did not memorize this from a textbook, but seeing was performing the function of seeing, and the pa~n~naa they had developed was the condition for understanding the truth of the reality at that moment.