Photographic Memory

In November 1890, Narendranath (pre-monastic name of Swami Vivekananda) went to Meerut. At that time, some of Narendranath's brother-disciples were staying in Meerut. One of them was Swami Abhedananda.
Narendranath had been a "voracious reader" from his childhood and used to spend much time in reading. Now, during the stay in Meerut, Narendranath, through brother disciple Swami Abhedananda, used to borrow and read one book from local library every day and return it the following day.
The local librarian was not ready to accept that Narendranath was reading the books, he thought that he was not reading anything at all and it was only an attempt to impress others. One day he clearly expressed his doubt to Swami Abhedananda.
Narendranath, upon hearing this, went to the librarian and told him, politely— "Sir, I have read all the books very attentively. If you have any doubt, you may ask me any question you like from these books we had borrowed."
The librarian asked him a series of questions and Narendranath correctly answered each of them. The librarian was highly surprised.