Manava Dharmashastra 4.48

4.48

sammukhīnatvādvāyvādīnāmaṅgaviprekṣitenāpi na mūtrayanpaśyet | vāyoścārūpatvādadarśanaṃ tatpreritaparṇaloṣṭādibhramaṇādavaseyam | vāyucakre tvayaṃ pratiṣedho viprayuktaḥ | sarvato hi vāyurvāti |

Medhātithi’s commentary (manubhāṣya):
What is meant is that one shall not do the act facing the wind; and the other things he shall not look at, while urinating, even by turning his body towards them. Since wind is colourless, its seeing can only he ascertained by seeing the flight of leaves, hits of earth and other things waft

ed by the wind. This prohibition would be incongruous if it applied to the entire air-circle (atmosphere); since wind is blowing everywhere.—(48)