Bhagavad Gita · 6.13

समं कायशिरोग्रीवं धारयन्नचलं स्थिरः।सम्प्रेक्ष्य नासिकाग्रं स्वं दिशश्चानवलोकयन्॥

samaṁ kāya-śhiro-grīvaṁ dhārayann achalaṁ sthiraḥ samprekṣhya nāsikāgraṁ svaṁ diśhaśh chānavalokayan

Holding the body, head, and neck erect and still, gazing at the tip of one's own nose, without looking in any other direction —

— Bhagavad Gita 6.13

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)