I acknowledge this graphic from the Net.
In this 103 dharana and 129 verse of Vigyana Bhairava Tantra Shiva says:
Wherever the mind is
Cast aside its support
Free of ripples reach Shiva
In this verse Shiva once again explains the mindless space from a different angle.
Our mind has senses as gateways. It is the senses who wander in the external world for food. The Yoga fifth limb of pratyahara (denial of food) addresses the problem of the wandering mind by denying it sustenance.
One of the most cogent explanations I have seen of pratyahara based on Yoga Sutra of Patanjali is in http://www.swamij.com/yoga-sutras-25455.htm.
Each of the 8 limbs of Yoga build upon the previous. The first limb Yama, universal conduct, lays down five principles to adhere to: truth, non violence, simplicity, no greed & walking the path of Brahman. The second limb Niyama lays down ten rules for daily observance, in addition to the five universal principles of conduct. The third asana, physical postures, enable us to start on training the body to achieve the goal of yoga, which is stilling the mind and integrating mind, body and spirit. The fourth pranayama, breath control, trains the mind to support the trained body. The fifth limb, pranayama, withdrawal of senses, is the next step in controlling the senses to still the mind. The five lead to the next three limbs of dharana, concentration; dhyana, meditation; and samadhi, disengaged union, collectively called samyama, integration.
What we need to note is that each limb depends on success of the previous step being followed, even if not fulfilled. They are not independent of one another. Yoga Sutra clearly says that prank, breath is a major factor in disturbing the senses, and therefore control of breath is essential to control the senses. Similarly, controlling the senses is essential to go further in concentration of the senses at one point, and this essential to focus on one thought in meditation, which then can lead to disengaging from ‘ego’ which causes the thought. The result is Yoga, Union.
The support that Shiva wants to cast aside is this. When we try to still the mind, it is from both external inputs through the senses and internally stored inputs that are played back. Even if we physically block our senses in a zero gravity space, impressions already stored will be played with all audio, video, kinesthetic, olfactory and gustatory sensations. Just try this and you will find how resourceful your mind is in escaping from efforts to still it.
If we follow through each impression, we will find that there is a root cause for each. This is the support Shiva talks about. Become aware of what creates the impression or the revival of the stored impression and delete it. Reliving the impression emotionally and cognitively with full awareness will relieve that impression. This is also the foundation of several psychological therapeutic processes, including in neuro linguistic programming, Gestalt, and CBT.
This is also the essence of Bhagavan Ramana’s Self Inquiry. Keep asking who is thinking, who is feeling this and the inquiry will lead to the support. The mere awareness of the support will delete it from the mind leaving you free.