Bhakti-rasāmṛta-sindhu .1.27
Blended reading (Sanskrit + English inline)
Regarding concentration of the eyesight on the tip of the nose, there is a statement in the Bhakti-rasāmṛta-sindhu by a devotee who observed this being performed by a yogī. He remarked, “This great sage is concentrating his eyesight on the tip of his nose, and from this it appears that he has already realized the eternal form of the Lord within himself.”
This verse describes a sage in the position of ātmārāma. Raising and lowering the head is a special anubhāva for this type of person. He can possibly relish the qualities of the Lord. This is understood from the following verse. ātmārāmāś ca munayo nirgranthā apy urukrame kurvanty ahaitukīṁ bhaktim ittham-bhūta-guṇo hariḥ All different varieties of ātmārāmas [those who take pleasure in ātmā, or spirit self], especially those established on the path of self-realization, though freed from all kinds of material bondage, desire to render unalloyed devotional service unto the Personality of Godhead. This means that the Lord possesses transcendental qualities and therefore can attract everyone, including liberated souls. SB 1.7.10
My note
Source: vedabase.io