My PDF is old, how many repetitions of the Mercury square and which mantra should be used?

Among the meditations there are several versions e.g. beginner, advanced. I would like to ask how these meditations should be placed in a development system. Should I do, say, a merkaba meditation and a twin snake every day? The meditations are very well described in JoS, but I couldn't find any...

I was wondering, is the lower Dantian the only Dantian? The middle one corresponds to the heart chakra and the upper one to the sixth chakra. In relation to the lower Dantian, it has been written about the relationship between Fire and Water (Sun chakra and Mars chakra) The Mars chakra is...