The state of Trance is Samadhi. As the iron becomes fire only in the mid of fire, so is the self. The self becomes Self in the state of Samadhi.
The difference between Meditation and Samadhi/Trance is that the meditator, mind, and object of Meditation are present in Meditation. In contrast, in Samadhi/Trance the soul is wholly absorbed in Supreme Soul. – Rig Veda.
“Samyak Sarvato Dhritam”
Complete absorption is Trance – Swami Dayananda Saraswati.
When Meditation happens, the pulse drops and the yogi can sit for seven days without moving. It is ecstatic. 2nd level of Dhyana Yoga sits for forty-nine days without moving. 3rd level of Dhyana, when the yogi sits for three years without moving, is Samadhi (Enlightenment).
Patanjali yoga sutra is a step-by-step guide for Yoga aspirants, suggesting ways of substituting the afflictions of the mind with the qualities of the mind to get to the state of Samadhi/enlightenment. With dedicated practice, commitment, and persistence, it is all possible.
Ashtanga Yoga helps to purify all the levels of self for complete transformation.