Chapter 6 · verse 11 · gita.yoga.org

Bhagavad Gita 6.11

शुचौ देशे प्रतिष्ठाप्य स्थिरमासनमात्मनः। नात्युच्छ्रितं नातिनीचं चैलाजिनकुशोत्तरम्

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.