The fourth modification of Pranayama transcends both internal and external reference.
Everything is a preparation for something else. In this case, Rishi Patanjali states that once we have mastered (i.e. maintain full awareness of the breath) and are flowing with the breath through breathing in (external to the internal), breathing out (internal to the external) and breath retention (being the pause between the in and out and the out and in breaths), a fourth stage will manifest itself of its own accord beyond our volition or effort. The breath becomes so slow and shallow through its regulation that it is hardly perceptible as if it has ceased altogether. In that somapsychic state everything comes to a standstill so to speak. The breath is naturally and spontaneously arrested together with the movements of the mind. In that arrested state, the mind is no longer making references to any internal or external references (inner or outer space) and experiences timelessness (no reference to past or future, purely present in the Here and Now without a location).
In order for this type of what could be described as a true existential experiential experience to come about, one needs under the guidance of a competent Guru be instructed in the proper use of body and mind to reduce their disturbances in daily life with the accompanying danger of bringing them into our Sadhana (hence the importance of the Yamas and Niyamas, prescriptions for living and being , and Swami Dr Gitananda Giri’s injunctions that Yoga is a step-by-step process and that there is no Yoga without the Yamas and Niyamas) and assiduously prepare the body and mind through Sadhana (through the ability to keep the body still and control the flow of the Life Force through the breath).
Yoga is truly the art (skill) and science (demonstrable results) of consciously aware effort together with surrender of one’s effort (being the path of non-resistance and flow) to bring about the liberation of one’s consciousness from all mind constructs. Then and only then can the Seer truly abide in himself or herself.
Our journey to liberation starts with that very resolve. It starts with the mindset and is fed by our ongoing resolve and Sadhana. Under proper guidance and practice, bit by bit our self-limitations and illusions will drop off of their own accord. No matter how busy we are or overwhelming
life appears to be, everyone can spare 20 minutes a day for concerted practice. And all will benefit. Your mind will be rested from its agitations and will become more efficient in all tasks.