Rudra-prasava-varṇana
The Manifestation and Naming of Rudra / Nīlalohita
तस्मात्कृष्टेन कुर्वीत पुरीषं मूत्रमेव च / न च्छायायां तथा मार्गे स्वच्छायायां न मेहयेत्
tasmātkṛṣṭena kurvīta purīṣaṃ mūtrameva ca / na cchāyāyāṃ tathā mārge svacchāyāyāṃ na mehayet
Therefore one should relieve oneself—stool and urine—only in a proper prepared place; one should not urinate in the shade, on the road, nor upon one’s own shadow.