Many places, many names.
They're implied to exist in Liber MMM as 'Occult Trances'; the one for gazing is touched on only.
My guess? OP of MMM didn't actually have any and only heard about them in passing.
I don't often speak about often, I will talk about the requirements to use:
All data will be read as true, even if false; as long as linked assertively with a conflicting or different data-set.
You can't swim against the tide; it is possible to make an object or construct move in a way it is not generally capable/biased to move in by barraging it with conflicting data/information.
It's important to understand this fully.
We all know it, very important to have a natural and not literal understanding of it in regard to how the world is experienced
Seriously, I know it is not politically correct to say this but some of these Arts will be unusable to a person who has disabilities.
Sight meditation requires both eyes, for example.
Projecting an inner-world and using an avatar of yourself inside of it will not develop these meditations.
It must be at this point in the Bardo, it must be with the body you have.
That being said I do not believe you need all of them, to reach the highest point with one is essentially the same as all of these paths converge.
When The Buddah used them, he used them in a specific order which seemed more important than actually having individual ones; I think I understand why but I don't want to talk about it unless I'm sure.
I mean I think having just one is enough, the others are maybe more convenient and allow for more options I guess..
Probably will take many months, maybe years to bring one of these to a high point, It's important to have free-time and to not be impatient.
It may require substances; for example I needed to use in order to exercise the stillness needed to awaken some.
I think in all of 'The Work' they may be the most rare and least known meditations.
Anything I could tell you about them would be just me, I cannot cite any resources on acquiring them outside of what I say.
However the 'Gazing' portion of MMM is a good starting tip; what I've said is also a good tip too.
Also worth noting, if you can develop one you can develop every other one using the same rough methodology EXCEPT for sense/smell, like I've said.
I mean the fact that I am not considering these as separate senses in this time but rather one sense divided should give you an idea of how much time I've put into this specifically.
Even Liber MMM, al