KAṬHA UPANISHAD · 2.3.16

शतं चैका च हृदयस्य नाड्यस्तासां मूर्धानमभिनिःसृतैका ।
तयोर्ध्वमायन्नमृतत्वमेति
विष्वङ्ङन्या उत्क्रमणे भवन्ति ॥ १६॥

śataṃ caikā ca hṛdayasya nāḍyastāsāṃ mūrdhānamabhiniḥsṛtaikā ।
tayordhvamāyannamṛtatvameti
viṣvaṅṅanyā utkramaṇe bhavanti ॥ 16॥

A hundred and one are the nerves of the heart and of all these only one issueth out through the head of a man; by this the soul mounteth up to its immortal home but the rest lead him to all sorts and conditions of births in his passing.

Sri Aurobindo · CWSA 18, p. 126