Chapter 6 · The Yoga of Meditation · Krishna said
Bhagavad Gita 6.13 — Straight and still
समं कायशिरोग्रीवं धारयन्नचलं स्थिरः। सम्प्रेक्ष्य नासिकाग्रं स्वं दिशश्चानवलोकयन् ॥
samaṃ kāyaśirogrīvaṃ dhārayannacalaṃ sthiraḥ | samprekṣya nāsikāgraṃ svaṃ diśaścānavalokayan ||
Meaning
Holding body, head and neck straight and still, he should gaze at the tip of his nose without looking around.