Verse
तत्रैकाग्रं मनः कृत्वा यतचित्तेन्द्रियक्रियाः ।उपविश्यासने युञ्ज्याद् योगमात्मविशुद्धये ॥
He should set in a pure spot his firm seat, neither too high, nor yet too low, covered with a cloth, with a deer skin, with sacred grass, and there seated with a concentrated mind and with the workings of the mental consciousness and the senses under control, he should practise Yoga for self-purification.
Gītā 6·12