Mahaperiyava was camping in MIT campus in Chennai and one day after Bhashan offered prasadam including kungkumam (vermilion) to the students coming in a line. After one student getting the prasadam and walking away from Him, Mahaperiyava summoned him back and asked him in Kannada language whether was he from Dharwar" a place north of Bangalore in Karnataka. The student replied in affirmative. He then asked the student per chance was his name Chandrasekhara or Chandramouli. The student with an exclamation said it was indeed Chandramouli. He also confirmed his age as 22 when he was posed that question. Then Mahaperiyava enquired about the welfare of his parents and blessed him again. The entire dialogue was in Kannada.
Chandramouli hesitatingly informed Him that was the first occasion he was seeing Him and how come Swami knew so much about him. Mahaperiyava told him that when He was camping in Dharwar about 23 years ago, a couple came to Him and sought His blessings for a baby. Paramacharyal blessed them. When He gave the prasadam to the couple, the husband applied the kungkumam in the forehead and then a small bit of it on his right shoulder in a fast moving action (Theethi kondaar )
Mahaperiyava told Chandramouli that he did the same kind of action after receiving prasadam from Him and so was immediately reminded of his fathers similar action. Also remembering their place, He just added the bits and derived his age too. He also figured that his parents, having been blessed after Chandramouleeswara pooja,would very likely named the baby as Chandramouli.
See even that small insignificant motion of hand has been captured in His mental framework and recalled effortlessly after so many years.