Who is Parangusa dasar and whose avatar he took? Any salient features about him in old puranas or scriptures?
JyEshtE anUrAdhAsambhUtam vIranArAyanEpurE gajavaktrAmsam AchAryam Adhyam NadamunimbajE
It so happened that a few Tirunagari SrI Vaishnavas came into town once and narrated the beautiful Thiru VAi Mozhi "ArA amudhE adiyEn udalAm". The last lines were "KurukUrch ChatagOpan kuzhalil maliyach chonna OrAyiraththil ippaththum mazhalai thIra vallAr kAmar maney NOkkiyarkE" Through thos wonderful tiruvAi mozhi, NAdamunigal came to know that these were only 11 songs among 1000 supposedly sung in favor of Kannan by KuruKuch ChatagOpan". Excitedly, SrI NAdamunigal asked the devotees if they knew all the 1000, but they sadly did not. They said that even though they were from Tirunagari, they had been touring all the divya dEsams and when they went to Tirukkudandhai and prayed to ArAvamudhan, they were graced with the 11 songs. They got the thIrtha prasAdam from NAdamunigal and departed from there.
There began the quest for the remaining pAsurams. NAdamunigal went to Tirukkudandhai and asked around, but no one knew anything beyond the 11 pAsurams. The next stop was AzhvAr tirunagari where he met a divine man by the name of ParAngusa DAsar. From him, he learnt 11 more paasurams starting with "Kanninun siruththAmbu" composed by Madurakavi Azhvar in praise of KurukUrch Chatagopan who is none other than NammAzhvar. ParAngusa DAsar suggested that NAdamunigal sincerely recite this paasuram 12,000 times with utmost devotion to the Lord to get his Graces. NAdamunigal was very sincere in his attempt and followed the instructions most fruitfully: At the bequest of PerumAl and PirAtti, NammAzhvar appeared before NAdamunigal and asked him what he wanted. An elated NAdamuni revealed that he wanted to know all the TiruvAi mozhis. Much to his surprise, he came to know that there were not just a 1000, but 4000 of them. The 1000 were just the Tiruvai mozhis of NammAzhvar, but the remaining were the works of the other 11 AzhvArs.
The other BhAgavatAs who witnessed this wondrous sight, shared an interesting story at that point of time.
At Azhwar Thirunagari, Nathamuni met Sri Parangusadasar, a disciple from the clan of Madurakavi who is the grand disciple of NamAzhwar. He explained the Kumbakonam incident and enquired on the Thiruvaimozhi hymns. Sri Parangusa stated that he also knew that there were 1000 such hymns by NamAzhwar. But expressed his agony that as he didn’t learnt those, he would only be able to tell the 11 hymns named ‘Kanninunsiruthambu’, made by Madurakavi on praise of Namazhwar. Sri Parangusadasar also voiced that if Nadamuni continue to meditate chanting those 11 hymns for 12000 times, Namazhwar would appear before him. Nadamuni with full faith and determination chanted Kanninumsiruthambu for 1200 times and heard NamAzhwar speaking through the idol form itself. NamAzhwar blessed Nadamuni with Thiruvaimozhi as he wished. Also preached him Ashtanga Yoga, Dvaya Mantra, ThiruMantra, Charamasolka and Vyasasutras. He also helped him to get all the 4000 hymns of 10 Azhwars.