Books on Rainbow body/Light body?

[Rokazulu]

I learned a bit about the Rainbow body and Light body from people like David Wilcock and William Henry.

However, there wasn't any detail that went into how the people who obtained their light body did so.

I was wondering if there was any books that gave techniques that would help you feel what that state would be like. Perhaps it is too lofty of an ideal right now, but I would still be interesting in learning more about it.

Here is a video on the rainbow body for those who want to know what I'm talking about:

https://www.youtube.com/watch?v=0yjM04PH56g