Taittiriya Upanishad 2.3

स वा एष पुरुषोऽन्नरसमयः | तस्येदमेव शिरः | अयं दक्षिणः पक्षः | अयमुत्तरः पक्षः | अयमात्मा | इदं पुच्छं प्रतिष्ठा ॥

sa va esha purusho'nna-rasamayah | tasyedam eva shirah | ayam dakshinah pakshah | ayam uttarah pakshah | ayam atma | idam puchchham pratishtha ||

This person is made of the essence of food. This is its head; this the right wing; this the left wing; this the self (body); this the tail, the foundation.

यह पुरुष अन्न-रस से बना है। यही इसका सिर है; यह दायाँ पक्ष; यह बायाँ पक्ष; यह आत्मा (मध्य-शरीर); यह पुच्छ अर्थात् प्रतिष्ठा।