Raja Yoga meditation is taught by Paramathma through a diamond merchant by name Shri Lekhraj whom Paramathma named as Brahma.
Paramathma showed the scenes of Heaven and hell and also showed him that he will be born a Shri Krishna in Sathya yug of the next Kalpa.
Why is Paramathma showing the scenes of Heaven and hell to Brahma and not to all others who practice Raja Yoga meditation.
It is because it is Brahma who is fighting Maya for the first time in Sangama Yuga. He has no predecessors who have first hand experience in fighting Maya. Maya is the unwanted and negative thoughts that are created in our mind. Maya is otherwise called as Ravana.
Today for those who practice Raja Yoga meditation we have centres across the globe, we have teachers to teach Raja Yoga.in case of any doubt we have resources to clarify our doubts.
Where as in case of Brahma he has only Paramathma, and if Maya disconnect the relationship with Paramathma and it would be very sad. So it becomes so vital for Paramathma to show the scenes of Heaven and hell and the birth that is going to taken sathya yuga.
So let us not complaint that we were not shown the scenes of Heaven and hell while we are learning Raja yoga meditation.