Chapter 6 · The Yoga of Meditation · Krishna said
Bhagavad Gita 6.11 — The meditation seat
शुचौ देशे प्रतिष्ठाप्य स्थिरमासनमात्मनः। नात्युच्छ्रितं नातिनीचं चैलाजिनकुशोत्तरम् ॥
śucau deśe pratiṣṭhāpya sthiramāsanamātmanaḥ | nātyucchritaṃ nātinīcaṃ cailājinakuśottaram ||
Meaning
In a clean place he should set up a firm seat for himself, neither too high nor too low, covered with kusha grass, a deerskin and a cloth.