There are anecdotal stories of people entering higher states of consciousness during near death experiences, extremely deep meditation, holotropic breathing exercises, etc.
Really creative people describe their most proud acts of creation as if the idea came from somewhere else. As if the concept arose independently and they tried their best to relay it into the real world.
As for the people on psychedelic drugs, they usually speak of the higher state of consciousness as being more real than the real world… which would make sense if our usual consciousness was a subset of something bigger.