In plain words
They themselves are the three guṇas. These three become one when you switch on the switch called dhyāna. Once they become one, Ānanda arises from within us alone. That is why they said, ‘Trijanma pāpa saṃhāraṃ, eka bilvaṃ śivārpaṇaṃ’. The three must become one. This itself is the trikūṭa sthala. To this very principle they have given the name dhyāna.
Samādhi is what teaches samatva
Now the last, samādhi. What does it mean? Samādhi is what teaches samatva. What does samādhi mean? Once Manas is dissolved, for him there is nothing but the vision of Brahman everywhere! In it oneness is attained. In it he looks on pain and pleasure, both, alike. He regards blame and praise, both, alike. He looks on gain and loss, both, as one. But in this there are two kinds of state. The state that comes when one makes Manas one with Divinity and experiences the holiness within Divinity is true samādhi. For one who, without morality and honesty, without fear and respect in society, enters into injustice, wrongdoing and misconduct and goes about with his own selfishness alone as his aim, blame and reproach are both the same! Whatever anyone may think, his heart does not waver. That is a heart of stone. A demonic heart. Here too, with no pairs of opposites, things stay in an even state. That is, the mind that does not bind itself at all to morality and honesty and behaves like a demon stays one and the same. But this is not the true principle of sameness.
Divine vision comes to the maharṣis who have experienced the state of saṃyama
They said that the oneness of these three, dhāraṇā, dhyāna and samādhi, the last of Aṣṭāṅga Yoga, is saṃyama.