Hatha Yoga Pradipika, 1:12, 14

The yogi should pratice hatha yoga in a small room, situated in a solitary place, being four cubits square, and free from stones, fire, water, disturbances of all kinds, and in a country where justice is properly administrated, where good people live, and food can be obtained easily and plentifully... Having seated in such a room and free from all anxieties, he should pratice yoga, as instructed by his Guru.