Swami Vivekananda in one of his talks mentions a person, Jalangiman Chetti, claiming he acquired some special powers from constant repetition of certain mantras.
Who is this person and what powers did he possess?
One way for attaining Bhakti is by repeating the name of God a number of times. Mantras have effect — the mere repetition of words. Jalangiman Chetti's powers are due to the repetition of the Mantra — repetition of certain words with certain ceremonies. The powers of the Astras or Bānas (missiles, arrows, etc.) of ancient war were due to Mantra. This is taken for granted throughout our Shāstras. That we should take all these Shastras to be imagination is superstition.
To obtain Bhakti, seek the company of holy men who have Bhakti, and read books like the Gita and the Imitation of Christ; always think of the attributes of God.
The Vedas contain not only the means how to obtain Bhakti but also the means for obtaining any earthly good or evil. Take whatever you want.