In the early part of 1882, a group of spiritualists from Calcutta heard about Sri Ramakrishna’s spiritual power. Spiritualists generally strive for psychic powers and enjoy using them. As it would be a considerable achievement to influence Ramakrishna, they went to the Dakshineswar temple garden to test him. They were told that Ramakrishna had gone for an evening walk to Jadu’s drawing room and met Ramakrishna, Dr.Pearychand Mittra, the leader of the group, introduced himself and the others, including Niranjan (Swami Niranjanananda), as spiritualists. Ramakrishna had the power to see inside a person as one sees an object inside a glass case. As soon as he saw Niranjan, the Master remarked, “This boy is very good extremely guileless.”Immediately Pearychand said:”Sir, he is my nephew. He can mesmerize very well, and he is a wonderful medium.”     Now, the spiritualists expressed a desire to use their power to mesmerize Ramakrishna. The childlike Master agreed, regarding this as a mere amusement; moreover, he wished to humble them. Ramakrishna sat on a chair and three spiritualists, including Niranjan and his uncle, began to wave their hands about him. After trying hard for an hour, Pearychand said: “Sir, you are a great soul with strong mind. We are incapable of mesmerizing you.” Then the Master got up and said privately to Niranjan, “Come her often,  do not get involved in this spooky business any longer. My boy, if you allow your mind to dwell on ghosts, you will become a ghost yourself. But, if you fix your mind on God, your life will be filled with God. Now, which of these are you going to choose?” “Well, of course, the latter,” replied Niranjan. Niranjan later severed his connection with the spiritualists, and treaded the path shown by Ramakrishna.

Source: God Lived With Them by Swami Chetanananda