I did some digging and found quite a few references regarding Waite's use of the phrase, "the way, the truth and the life." The following should be enough to give a sense as to what he means; it's the mystic "path of attainment." This helps clarify his statement in the PKT, "This is in all simplicity the card of human love, here exhibited as part of the way, the truth and the life."
"I have no need to affirm that the secret tradition, either in the East or the West, has been always an open secret in respect of the root-principles concerning the Way, the Truth and the Life."—Occult Review, vol. 8, no. 4, October 1908, "The Hermetic and Rosicrucian Mystery."
"It is idle to decode books of secret doctrine unless they have something more definite to tell us concerning the way, the truth and the life."—The Secret Doctrine in Israel, "The Mystery of Shekinah," pg. 227.
"There is no question that Mysticism is much simpler on a pure theistic basis than on any Trinitarian hypothesis, but the Christ-process remains the Way, the Truth and the Life from either doctrinal standpoint."—The Way of Divine Union, ch. 16, The Way of Attainment, pg. 320
"By a dispensation given from above, as from a Great and Holy Assembly, abiding in a Sanctuary not made with hands, hidden within the Veil, the Hierarchic Mystery of Christ was declared in space and time, by the manifestation of our Lord and Saviour. He is to us in an especial manner the Great Exemplar of initiation—its way, its truth and its life. He exhibited the path and term, no longer in Rites and Symbols, but in the form of life. . ."—Fellowship of the Rosy Cross Adeptus Minor Initiation
"In the Grade of Adeptus Minor the Postulant is put definitely on the Path of Attainment, understood as the Way, the Truth and the Life which are in Christ. . . ."—Fellowship of the Rosy Cross Adeptus Minor Initiation