SB 7.3.2
sa tepe mandara-dronyam
tapah parama-darunam
urdhva-bahur nabho-drstih
padangusthasritavanih
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
In the valley of Mandara Hill, Hiranyakasipu began performing his austerities by standing with his toes on the ground, keeping his arms upward and looking toward the sky. This position was extremely difficult, but he accepted it as a means to attain perfection.