Vignana Bhairava Tantra - 128

Focus on the void

नित्ये निराश्रये शून्ये व्यापके कलनोज्झिते |
बाह्याकाशः मनः कृत्वा निराकारं समाविशेत् ||

Let the mind focus on the eternal, the independent void, spread everywhere, with no possibility of calculating its length, breath and height. In this space outside, place your mind and enter the spaceless void completely. - SS. 

Vignana Bhairava Tantra - 127

Meditate on the unknowable Self

यदवेद्यं यदग्राह्यं यच्छूनयं यदभावगं|
तत्सर्वं भैरवं भाव्यं तदन्ते बोधसंभवः ||

Yadavedyam yadagrahyam yacchoonyam yadabhavagam|
Tatsarvam Bhairavam Bhavyam Tadanthe Bodhasambhavah||

All that which remains unknown and cannot be known, all that which can neither be held nor grasped, all that which remains as a void and all those unimaginable possibilities which have no existence - everything should be contemplated as Bhairava. At the end of such contemplation - true knowledge unfolds. - SS