There is an interesting book in Hindi published by Gorakhnath-mandir (in Gorakhpur), its title is गोरक्षनाथ और नाथ सिद्ध / Gorakṣanāth aur nāth siddh. There is written following:
आजकल हम विभिन्न प्रकार के योगों के नाम सुनते हैं – राजयोग, हठयोग, ज्ञानयोग, लययोग, भक्तियोग और कर्मयोग| ये शब्द आधुनिक शब्द हैं | प्राचीन योगियों की इसमें आस्था नहीं हैं |
In modern time we have heard about many varieties of Yoga: rajayoga, haṭha-yoga, jñānayoga, layayoga, bhaktiyoga, also karmayoga. These terms are modern. Ancient yogis did not believe this.
I do not think that all these varieties are completely modern, however, in this statement there is much truth. A person who is limited to a vision of yoga in only one category, is unlikely following the right yogic direction. While modern styles of “haṭha–yoga” sin even more, they often lead away from the main yogic goals, they are feeding people’s ego instead of giving liberation from it. They create confusion in the people’s minds, instead of freeing oneself from it. And this mass situation is paradoxical, as often what is called yoga, on the contrary, leads away from the yogic path. Yoga is the integrity of own nature, and how you will come to this and call it is a secondary importance think. It is no coincidence that the term upāya can be translated both, as a method, as a ruse or a trick.
It seems to me that between such a Vedic or Vedantic principle as नेति नेति (neti-neti – «neither this nor that») has much in common with द्वैताद्वैत विलक्षण (dvaitādvaita vilakṣaṇa) in the Nātha Tradition. The second is often found in the Sanskrit texts of Nāthas. In the later Nātha text in Hindi, Gorakh Sabadi, this principle is represented as अलख (alakh) – from the Sanskrit अलक्ष अ-लक्ष (a-lakṣa, i.e. «transcendence beyond the limits of symbols»).
अन्तर्लक्ष्यविलीनचित्तपवनो योगी यदा वर्तते
दृष्ट्या निश्चलतारया बहिरधः पश्यन्नपश्यन्नपि ।
मुद्रेयं खलु शाम्भवी भवति सा लब्धा प्रसादाद्गुरोः
शून्याशून्यविलक्षणं स्फुरति तत्तत्त्वं पदं शाम्भवम् ॥ ३७ ॥
antarlakṣyavilīnacittapavano yogī yadā vartate
dṛṣṭyā niścalatārayā bahiradhaḥ paśyannapaśyannapi |
mudreyaṁ khalu śāmbhavī bhavati sā labdhā prasādādguroḥ
śūnyāśūnyavilakṣaṇaṁ sphurati tattattvaṁ padaṁ śāmbhavam || 37 ||
By the grace of the Guru, when the consciousness and energy of Yogī are absorbed by the inner aim, perception (vision) is directed to the outside and motionless, but at the same time, suspended from vision; this mudrā known as śāmbhavī. That radiant essence beyond (vilakṣaṇam) of emptiness (śūnya) or fullness (aśūnya), is known as the Śambhū state (Śiva or the embodiment of appeasement).
Thuse, according to the Nātha Yogīs doctrine, to be beyond emptiness or fullness – means to be both emptiness and fullness simultaneously.