He was seated on a deerskin and was practicing all forms of austerity. Because his body was smeared with ashes, he looked like an evening cloud. On his hair was the sign of a half-moon, a symbolic representation.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
लिङ्गं च तापसाभीष्टं भस्मदण्डजटाजिनम् । अङ्गेन सन्ध्याभ्ररुचा चन्द्रलेखां च बिभ्रतम्
liṅgaṃ ca tāpasābhīṣṭaṃ bhasmadaṇḍajaṭājinam | aṅgena sandhyābhrarucā candralekhāṃ ca bibhratam
SB 4.6.36