It is believed on one Thai Amavasyai day, a traveling sage named Salihotran arrived in Thiruvallur and encountered a congregation of sages. They were bathing in the tank Hrith-Thapa-Nasini, and he was encouraged to bathe before doing his daily rites.
The bath changed his mind, and Sri Salihotran resolved to stay on the bank of that Holy tank and begin a one-year penance without food or drink. On the same Pushya Amavasya day the next year, he fulfilled his penance, took a holy bath in the Hrith-Thapa-Nasini tank & completed
his morning rituals. As he was fasting for one year without food and drink, he collected on that day some paddy and prepared prasadam using rice flour. Lord Narayana appeared as an old Brahmin and approached Salihotran, who was about to serve a visitor.
The Brahmin ate his offering right away. Salihotran saw the old Brahmin was starving and offered his share to the guest. Guest left satisfied. Another year of fasting followed. Salihotran bathed and cooked again on Pushya Amavasya.
Salihotra Maharishi requested that the Lord stay there and bless and heal anybody who prays to him after bathing in the tank. Thus Sri Vaidhya Veeraraghava Swamy. Even today all the bhakts who visit the temple offer gur(jaggery) to swami and mix it in the pushakarani.