Bhagavad Gita 6.11
शुचौ देशे प्रतिष्ठाप्य स्थिरमासनमात्मनः।
नात्युच्छ्रितं नातिनीचं चैलाजिनकुशोत्तरम्।।6.11।।
Shuchau deshe pratishthapya sthiramasanamatmanah
Natyuchchhritam natinicham chailajinakushottaram
Simple meaning, written by AIIn a clean place, he should set up a firm seat for himself, neither too high nor too low, spread with cloth, deerskin and kusha grass.