I've been reading some Bardo Thodol texts lately and it has a Padmasambhava treasure text about introducing the true nature of mind. It is quite positive about stating that such a realisation is the highest, all inclusive method, so no need for anything else. But that's just something I wanted to mention.
The other thing is that it was brought up how the nature of mind is introduced even before the development stage beings. In the Vairocanabhisambodhi Sutra (in Tibetan tradition: a text of the outer carya tantras) in the first chapter the nature of mind is introduced and then all the mantra-mandala-ritual stuff begins from chapter two. So if Mahamudra/Atiyoga is a special practice on its own right, I guess it can be practised without other practices.
The Buddha said, “Lord of Mysteries, it is in one’s own mind that one seeks bodhi and omniscience. Why? Because its original nature is pure. The mind is neither within nor without, nor can the mind be apprehended between the two. Lord of Mysteries, the Tathāgata, worthy [of worship] and perfectly and fully awakened, is neither blue nor yellow nor red nor white nor crimson nor the color of crystal, neither long nor short nor round nor square, neither bright nor dark, and neither male nor female nor neuter. Lord of Mysteries, the mind is not of the same nature as the realm of desire, nor is it of the same nature as the realm of form, nor is it of the same nature as the realm of non-form, nor is it of the same nature as the destinies of gods, nāgas, yakṣas, gandharvas, asuras, garuḍas, kiṃnaras, mahoragas, humans, or non-humans. Lord of Mysteries, the mind does not reside in the realm of the eyes, nor does it reside in the realms of the ears, nose, tongue, body, or mind, and neither is it visible, nor does it manifest itself.
“Why? [Because] the mind, which has the characteristic of empty space, is free from all differentiation and nondifferentiation. Why is that? That whose nature is the same as empty space is identical to the mind, and that whose nature is the same as the mind is identical to bodhi. In this manner, Lord of Mysteries, the three entities of mind, the realm of empty space, and bodhi are without duality. They have compassion as their root and are fulfilled by the pāramitā of expedient means. For this reason, Lord of Mysteries, I teach the dharmas in this manner so as to make the multitudes of bodhisattvas purify the bodhi-mind and know their mind.
“Lord of Mysteries, if a man of [good] family or a woman of [good] family wishes to know bodhi, they should know their own mind in this manner. Lord of Mysteries, how is one to know one’s own mind? It cannot, namely, be apprehended by seeking it in distinctions, or colors, or shapes, or external objects; or in form or sensation, ideation, volition, or consciousness; or in ‘I’ or ‘mine’; or in the grasper (i.e., subject) or the grasped (i.e., object); or in the pure; or in the [eighteen] elements [of existence] or [the twelve] sense fields; or in any other distinctions.
(Vairocanabhisambodhi Sutra, ch. 1, tr. RW Giebel)
"If the Buddha-Nature is seen, there will be no seeing of a nature in any thing."
(Nirvana Sutra, T12n374p521b3; tr Yamamoto)
"Neither cultivation nor seated meditation — this is the pure Chan of Tathagata."
(Mazu Daoyi, X1321p3b23; tr. Jinhua Jia)
“Don’t rashly seek the true Buddha;
True Buddha can’t be found.
Does marvelous nature and spirit
Need tempering or refinement?
Mind is this mind carefree;
This face, the face at birth."
(Nanyue Mingzan: Enjoying the Way, tr. Jeff Shore; T2076p461b24-26)