Both Jiva Goswami in his Bhagavata Sandarbha and Krishnadasa Kaviraja in his Chaitanya-Charitamrta look to Shripad Vishnuswami for inspiration to establish the essential difference between God and the individual souls and quote from his Sarvajnasukta, his commentary on Vedanta.
Vishnuswami is the founder-acharya of the Rudra sampradaya and is the oldest of the four recognized sampradayas. It is even said that Vishnuswami was born in the Dravida country after the completion of the sacrifice of Janamejaya around the beginnining of Kali-yuga.
Although most scholars are only able to find scanty and conflicting information on Shripada Vishnuswami, Shrila Bhaktisiddhanta Saraswati Thakura gives us an authoritative biographical account of Vishnuswami which we accept to be accurate.
There were three Acharyas bearing the name of Vishnuswami in the Rudra sampradaya. The first is called Adi Vishnuswami who is said to have been born about the third century B.C. in the Pandyan country. Vishnuswami's father Deveshvara was the royal priest and minister. Devatanu, as he was known before he took the sannyasa name of Vishnuswami, was trained by his father in a vigorous theistic education, to fight Buddhism. The Pandyan king exerted all his influence to crush Buddhism in particular and other non-Vaishnava sects in general. King Pandyovijaya and his minister, Deveshvara, went to Puri and recovered the Deities of Jagannatha, Balarama and Subhadra, which had been turned into the Buddhist Dharma by Buddha and Samgha by the Buddhists. King Padyovijaya and Deveshvara removed the Deities from the main Temple to sundaracala about two miles away by cart. This is said to be the origin of the Rathayatra of Jagannatha. Now the ceremony of conveying the Deities from the Temple to the car is named Pahandi or Panduv ijaya. The word Panda is applied to the priests of Jagannatha and is said to be derived from the "Pandya". The Deities were again brought back to the Temple after Buddhism had been supressed to some extent.
Vishnuswami was the first to adopt tridandi sannyasa which he brought into practice among his seven hundred sannyasa disciples. It was he who introduce the Ashtottara satanami sannyasa (108 designations of sannyasis) including the dasanami which was adopted by Shankara in his sect. It was not Shankara who originated it as some scholars think. Vyasheshvara was the last in the line of Sannyasis, after whom the line became almost extinct, until it was revived by Raja Gopal who also assumed the name of Vishnuswami in the beginning of the 9th century. His main follower was Bilvamangala.
Raja Gopala Vishnuswami revived the old Vishnuswami line and began the active propaganda with renewed vigour and enthusiasm. He installed the Varadaraja Temple in Kanchi, Ranchorlal in Dwaraka and many other Deities in different places of pilgrimage. He converted many of Shankara's prominant disciples after Shankara's death.
After the disappearance of the second Vishnuswami a great feud took place between his community and that of Shaiva Shivaswami who regards Rudra as an independant God while the former holds Rudra as Guru and the intimate associate of Vishnu. The Shaiva opposed it vigorously and people failing to appreciate the subtle point of theism in the Shuddhadvaita system of Vishnuswami, became inclined to Shaivite monism, which soon became embraced by the population in general. The Shaivaite community taking advantage of the situation, tried to misappropriate Vishnuswami's Sarvajnasukta and modified it to a great extent to suit their system.
The third revival came under Andhra Vishnuswami in the 13th century whose successors included Lakshmana Bhatta, the father of Vallabhacharya. This Vishnuswami is said to have been the son of a minister of a Dravidian prince under the Emperor of Delhi.
Vishnuswami's philosophy is Vishuddhadvaita.
The fourth Vaishnava acharya, Vishnuswami, representative of the Rudra sampradaya (who worship the avatara of God known as Narasimhadeva) is less known than the other three.
Actually there is some confusion about him, as it seems there have been three Vishnu Swamis: Adi Vishnu Swami (around 3rd century BCE, who introduced the traditional 108 categories of sannyasa), Raja Gopala Vishnu Swami (8th or 9th century CE), and Andhra Vishnu Swami (14th century).
The emphasis of this school, called shuddha-advaita ("pure monism"), is on the concept of lila or the pastimes by which God can be transcendental and immanent according to His will. Thus everything is pure, including the material universe, that is created by God and intimately related to Him. In his method of worship, Vishnu Swami gives prominence to Rama, the previous avatara before Krishna.
Vishnu Swami visited Puri and founded there the Jagannatha Vallabha Math in the gardens of the Temple, where Ramananda Raya also established his spiritual school. Among the famous followers of this sampradaya we can mention Shridhara Swami (who became famous for his commentary on the Bhagavata purana).
Source : http://www.4sam.org/rudra/vishnuswami.html