Charles Webster Leadbeater,
The Inner Life: volume II — Fourth Section…
“ The trained seer, who is able to sense the chord, attunes his own vehicles for the moment exactly to its notes, and then by an effort of will sends forth its sound. Wherever in the three worlds that man who is sought may be, this evokes an instantaneous response from him. If he be living in the physical body, it is quite possible that in that lower vehicle he may be conscious only of a slight shock, and may not in the least know what has caused it. But his causal body lights up instantly ”
