On the high end of meditation, there is fantastic perceptions of various orders of reality and there is also total non-perception, where there is nothing but existence without form distinction.

This may be considered to be spiritual (supernatural) form and formlessness. When the dog trainer blows the dog whistle, the human beings say that they hear no sound but when the traffic police blows a whistle, the human say that they hear a sound. In either case there is sound but while the dog is equipped sensually to hear certain frequencies, the human being lacks the faculty

In meditation if one clambers to perceive supernatural objects and one is not content to not perceive them, one will become dishearten and will turn away from the practice and resume something solid which is physical reality from which we are never frustrated because the forms are definite and familiar.

A yogi must be satisfied with both form and non-form in meditation. This allows for a settled mind and an equipoise attitude which is needed for him to develop the higher senses which can perceive what is formless or what appears to be formless.

It takes time to develop the perception. If the yogi becomes frustrated early on, he will become impatient and will not do sufficient practice. A kitten does not see as soon as it is born, it takes some weeks before its eyes open and they develop perception. Hence initially the kitten only has the black sphere in a black space, which mean there is no distinction for anything. But later if the kitten survives, then it will have the blue sphere, where there is distinction in the same state which before seemed to be formless.

The problem is that for the kitten it is a few weeks but for the yogi, there might be blankness, voidness, formlessness, or nothingness, for months or even lives of meditation until finally, at last, the supernatural perception develops.

Who can wait that long?