It’s a joke. In Lovecraft novels the protagonist pokes around ultimate reality and finds madness therein. It’s not claiming anything specific about meditation.

After a particularly horrific trip on DXM, some of Lovecraft's writing was by far the best description of what I went through mentally. I remember my jaw dropping when reading a few Lovecraft passages that seemed to perfectly capture my mental state and the horror of it.

Was it because Lovecraft had any special insight into reality? Nope, not at all. But he had insight into some of the horrors that can emerge from the depths of our own minds. Probably partially because, like you said, he was a little bit crazy.