In the hindu sacred text Guru Gita is said that to meditate and pray while seated on a seat of wool brings all attainments.
In some yoga traditions the Guru Gita is considered to be an “indispensable text”.
You can read here the complete Guru Gita verses about praying while seated on different materials:
137. Repeating it (the Guru Gita) while seated on cloth brings lack; on stone, disease; on the earth, unhappiness; and on wood, it becomes useless.
138. Repeating it while seated on a black deerskin, one attains knowledge; while on a tiger skin, the treasure of liberation. Sitting on sacred kusha grass brings wisdom, and a seat of wool brings all attainments.