Bhagavad Gita 6.11

शुचौ देशे प्रतिष्ठाप्य स्थिरमासनमात्मनः। नात्युच्छ्रितं नातिनीचं चैलाजिनकुशोत्तरम्

śhuchau deśhe pratiṣhṭhāpya sthiram āsanam ātmanaḥ nātyuchchhritaṁ nāti-nīchaṁ chailājina-kuśhottaram

In a pure place, established on a fixed seat of his own, neither very much raised nor very low, made of a cloth, a black antelope skin, and kusha grass, one over the other;