There's a copy of the referenced article here: The Religious and Medicinal
Uses of Cannabis
in China, India and Tibet by MIA TOUW.
The relevant quote from the article (which was copied into Wikipedia) is,
Tantric Buddhism, which flowered in the TibetoHimalayan region, cannabis is an important part of the
meditative ritual which may or may not include sexual
intercourse. It is taken to facilitate the meditation and
heighten awareness of all aspects of the ceremony. The
large dose, taken orally, is timed so as to ensure
increasingly heightened awareness from the beginning of
the ritual onwards, with the greatest "high"-delayed when
taken orally by about an hour and a half- coinciding with
the climax of the ceremony (Bharati 1965). Secular use, both medicinal and
recreational, is equally widespread but, as Sharma (1977b)
notes, cannabis is taken for granted in the Himalayas and
therefore is not much discussed.
The "Bharati 1965" reference is
Bharati, A. 1965. The Tantric Tradition. London: Rider & Co.
There's a Wikipedia article about the author of that reference -- Agehananda Bharati.
The book is available for bout $20 from Amazon -- The Tantric Tradition Mass Market Paperback – January 1, 1970