BṚHADĀRAṆYAKA UPANISHAD · 4.3.35

तद् यथानः सुसमाहितम् उत्सर्जं यायाद् एवम् एवायं शारीर आत्मा प्राज्ञेनात्मनान्वारूढ उत्सर्जं याति ।
यत्रैतद् ऊर्ध्वोच्छ्वासी भवति ॥

tad yathānaḥ susamāhitam utsarjaṃ yāyād evam evāyaṃ śārīra ātmā prājñenātmanānvārūḍha utsarjaṃ yāti ।
yatraitad ūrdhvocchvāsī bhavati ॥

'Now as a heavy-laden carriage moves along groaning, thus does this corporeal Self, mounted by the intelligent Self, move along groaning, when a man is thus going to expire.