Katha Upanishad - Verse 2.3.16
Text: शतं चैका च हृदयस्य नाड्यस्तासां मूर्धानमभिनिःसृतैका । तयोर्ध्वमायन्नमृतत्वमेति विष्वङ्ङन्या उत्क्रमणे भवन्ति ॥ १६ ॥ śataṃ caikā ca hṛdayasya nāḍyastāsāṃ mūrdhānamabhiniḥsṛtaikā | tayordhvamāyannamṛtatvameti viṣvaṅṅanyā utkramaṇe bhavanti || 16 || 16. A hundred and one are the nerves of the heart. Of them, one has gone out piercing the head; going up through it, one attains immortality; others at the time of death lead different ways. Shankara’s Commentary: It has been stated that there is no going; for, the knower who has attained the knowledge that the atman is the all-pervading Brahman devoid of all attributes and who has untied all the knots due to ignorance, &c....