Though one may not find many accounts of the Stong-ra and physical exercises in the main Tantras, these are the pith-instructions taught by the masters. Furthermore, in the practice on Rtsa[r_nar:56] and prana it is sometimes difficult to attain Samadhi through the gentle or soft practice; therefore, the radical or strong practice is needed. In that case it is believed that these preparatory practices will minimize hazards and obstacles.

The Actual Successive Practice of the Path

This is expounded in two sections: The classifications of the Path; and the instruction of entering into the Path.

There are different ways to classify this teaching--some divide it into two groups; some, into three, four, six, or ten. However, from the viewpoint of befitting the different dispositions or capacities of human beings, the teachings can be classified in three groups. First, the teaching that enables one to become the perfect Buddha in this very life; second, the teaching that enables one to become Buddha in the Bardo state; third, the teaching that enables one to become Buddha in future lives[r_nar:57]. From the viewpoint of the nature of the practice, the teaching can be divided into the ordinary Perfecting Yoga, and the outstanding betterment practice of the Perfecting Yoga The latter is not usually found in the teachings of the masters of this school (Kar-gyupa), who mainly depend on the pith-instructions alone.

However, those masters in the Marpa school who held the tradition of preaching the Tantra do accept this type of teaching.

Marpa said:

"From the great master Naropa, the guard[r_nar:58],
I have heard the profound Tantra of Hevajra
I also received the pith-instruction of joining, transformation and unification[r_nar:59]
(Bsre, rpo, nrtsams-sbyor).
Especially have I learned the teaching of Heat Yoga and Karmayoga.
Thus, for me, was the essence of the teachings of the Whisper Succession illustrated."

Thus, Marpa said, was illustrated for him the joining and transformation practice of the Whisper Succession. In particular, he relied on the practice of the Heat Yoga of the Vajra, which produces the four blisses. Later on, through the practices of Karmayoga, the four blisses were also raised within him. From this we know that, in the teaching of Hevajra, he relied mainly on the Heat Yoga and Karma-yoga.

Again Marpa said:

"In the city of Lagkedar, in the west,
I bowed down at the feet of the holy
Ye-shes-snying-po.
From him I heard the teaching of
Gsun-wa-adus-b'a of the Father Tantra[r_nar:60].
And also received the pith-instructions
Of the Illusory Body and Great Light.
Thus have I learned the teaching of the
Path of the Five Steps."

According to Naropa there are four outstanding Tantras