Lord  Vishnu's Sreevasthalam  

 Vilvamangalamswamigal was a great devotee of Unni Kannan .Kannan used to play pranks with him every now and then.One day as he was preparing unni appam
to offer Unni kannan,a neighbouring boy came and ate appam and took
some. Vilvamangalaswamigal caught the boy red handed and in anger
punished him by keeping a hot rod on his cheek.Thus the boy got burns
and went home crying.As Vilvamangalam was doing Puja the next day unni
kannan came before him with burnt scar on one of his cheeks.At once
Vilvamangalam realised that the boy who came to the kitchen was no other
than unni kannan himself in disguise of the boy.

    
To meet Lord Vishnu,Sage Narada went to Vishnu Loka.There he saw a scar
on Lord   Vishnu's cheek.Lord said that He was keeping the scar as a remembrance  of his devotee Vilvamangalam.Lord Vishnu is having another scar in
his chest which is known Sreevathsalam.The reason for the scar as
follows.   
  
There arose an arguement as who has the maximum patience,Brahma,Vishnu or Siva.No
one could solve their doubts.So the sage Bhrigu was made to clarify
their doubts.The sage went to Brahma and tried to enter his room
without permission ,but Lord Brahma in rage drove him out.Next he went
to Lord Siva and tried to provoke His anger to test him.Siva got angry
and chased him out.In the end he visited to Lord vishnu,who was
sleeping undisturbed So theSage Bhrigu Jumped up and down on his chest
to test Him.
    Lord Vishnu opened His eyes and bore  the pain  with maximum patience .The chest of Lord Vishnu has a scar even today which is known as Sreevasthalam(scar in His chest),as a remembrance of the sage Bhrigu.
   The sage Bhrigu was a famous astrologogical  system followed even today