Bhagavad Gita 6.11

शुचौ देशे प्रतिष्ठाप्य स्थिरमासनमात्मनः।नात्युच्छ्रितं नातिनीचं चैलाजिनकुशोत्तरम् ॥६.११॥

śucau deśe pratiṣṭhāpya sthiramāsanamātmanaḥnātyucchritaṃ nātinīcaṃ cailājinakuśottaram

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.

गीता