In some advanced meditations one can arrive at a vision of oneself myself ‘pouring’ life energies into a hole in the ground with ‘this world’ inside it.
This is similar to the hourglass model but what is used in measuring is not some sand but one’s own energy flow.
This is strongly related to the ‘back flow initiation
However, he we are applying Vortex Breathing with an inversion: during exhale the energy of breath is normally pushed into a black hole (observable after some time of practicing). Now, one can create a ‘recoil’ force by breathing out strongly with half-closed lips like when filling a balloon.
The recoil will push awareness back to the outside… like pulling one’s head outside the sand..