Yoga Sutra 3.12 transformation of one-pointedness
In that (samādhi) the sameness of the idea which has subsided and the newly risen idea in the mind is its transformation of one-pointedness
In the concentrated mind, the earlier idea having subsided, the next idea which rises is similar to it. The mind in samādhi assumes the form of both of them. This is repeated in just the same way till the breaking of the samādhi. Of the mind which possesses that characteristic: this is the transformation of one-pointedness.
In that time of samādhi the sameness of the idea which has subsided and the newly risen idea in the mind is its transformation of one-pointedness. In the concentrated mind whose mental process is inhibited from going out the earlier idea subsides is subdued: the next idea which rises appears is the same. The concentrated mind means a mind in the state of samādhi, which is distinguished by concentration (samādhāna); The mind in samādhi assumes the form of both the ideas, the subsided and the newly risen. This is repeated in just the same way: the first idea having subsided, a further one of similar nature is born, and when that has subsided yet another rises, and when that too subsides, still another rises, and so till the breaking of the samādhi, up to the breaking of the samādhi by a saṃskāra of extraversion. Of the mind which possesses the characteristic, of assuming the form of subsidence and rise of similar ideas every instant, this is the transformation of one-pointedness.
Of these three transformations (inhibition, samādhi, and one-pointedness), the inhibitive transformation is the state where the mind is saṃskāra-s alone, as a result of inhibition of external mental processes (bāhya-vṛtti).
The samādhi transformation is from inhibition of external ideas (pratyaya), moving towards inhibition of all ideas but before total inhibition of ideas. For there will be no rise of one-pointedness at the later stage of inhibition of all ideas.
Then the one-pointed transformation is the similarity of the next thought to the one that has just subsided, which is possible only at the time of samādhi.
The three have been presented in an order so that a later one is interior to an earlier one.
(Opponent) What is the point of setting all these out?
(Answer) The purpose is meditation, on detachment. For it is all movement of the guṇa-s, and its character is nothing but change of guṇa-s. Also there is the purpose of teaching that knowledge of the past and future arise from saṃyama on the three transformations.