Brahma has four heads from which He spoke the four vedas – the Rig Veda, Yaju Veda, Sama Veda and Atharva Veda. When the three guna (Satva, Rajas and Tamas) manifest, they do so in a combination such that either one of the three predominates or they are in a confused proportion where neither predominates. This results in four types of ‘Guna manifestation’ as explained by Parasara in his monumental classic Brhat Parasara Hora Shastra.