Bhagwad Gita
Chapter 6, Verse 11
शुचौ देशे प्रतिष्ठाप्य स्थिरमासनमात्मनः।
नात्युच्छ्रितं नातिनीचं चैलाजिनकुशोत्तरम्।।6.11।।
In a clean spot, having established a firm seat of his own, neither too high nor too low, made of cloth, skin, and kusha grass layered one over the other.