The Astral Plane, Its Scenery, Inhabitants, and Phenomena
by C.W. Leadbeater
1895

EXCERPT FROM INTRODUCTION:

...every precaution in our power has been taken to ensure accuracy, no fact, old or new, being admitted to this manual unless it has been confirmed by the testimony of at least two independent trained investigators among ourselves, and has also been passed as correct by older students whose knowledge on these points is necessarily much greater than ours. It is hoped, therefore, that this account of the astral plane, though it cannot be considered as quite complete, may yet be found reliable as far as it goes...The first point which it is necessary to make clear in describing this astral plane is its absolute reality. Of course in using that word I am not speaking from that metaphysical standpoint from which all but the One Unmanifested is unreal because impermanent. I am using the word in its plain, every-day sense, and I mean by it that the objects and inhabitants of the astral plane are real in exactly the same way as our own bodies, our furniture, our houses or monuments are real...