I used the Search feature for “3 sun meditation” and the top result other than this thread is the original posted tutorial by @AdamThoth
That means it’s unique to him and this forum, though I have it in my head he might be an author and perhaps it’s in one of his books.
Did you try the Adam Thoth tutorial yet, starting with the instructions for the void meditation? You follow the part from the text “The first phase of the meditation is the three sun meditation” onwards.