When speaking about emptiness (śūnya), the very first thing that comes to mind in connection with the Nāthas is the ślokas from the Siddha-siddhānta-paddhati (Upadeśa 6, Śloka 9):
चित्प्रकाशपरानन्दौ यस्य वै कुण्डलद्वयम्।
That whose two kuṇḍalas are the light of consciousness and the supreme bliss, whose rosary is the calmness of the gaze (immersed in the Ātman), is called avadhūta.
It is about the earrings, which are often called “kuṇḍala, darśana, mudrā”, are spoken of as the light of the highest consciousness (citprakāśa) and the highest bliss (parānanda). It can be said that out of 36 tattvas of Śivadarśana, these are the two highest principles of Citśakti or Prakāśa (Śiva) and Ānanda Śakti (Vimarśa or Śakti, reflecting the greatness of Śiva). Judging by the mantra associated with the kuṇḍalas of the Nāthas, the power of space, khecarī or the heavenly power (spatial) and the earthly bhūcarī are mentioned there. Mudrā in one of the interpretations from the basis “mud” – ‘to mix,’ ‘to connect,’ i.e. that which unites the main polarities. This can be the fusion of japa and ajapa, prāṇa and āpaṇa, sun and moon, nāda (vibration) and anāda (silence), Śiva and Śakti, śunya (emptiness) and pūrṇatā (fullness, abundance) in oneself. In essence, this level of realisation implies the realisation of the fusion of the main polarities and being in a state above which there is nothing (anuttara). Here, of course, we are not talking about just a piercing, which even hippies can do for themselves, the value is only in the “piercing”, “absorption” of the basic elements in each other. Such a yogi, right in the place where he is, can gain knowledge of everything that is in the “brahmāṇḍa” (macrocosm). Physically, kuṇḍalas can be made of different materials, they can symbolise alchemical principles (internal alchemy), but this is already beyond the scope of a short explanation. Internal alchemy is what a realised Guru teaches spiritually matured students and, in any case, the basis of everything is the fusion of polarities, i.e. the realisation of yoga.