Three levels of sleep
FMC00.248 provides a synthesis linking the three levels of sleep or Sleep States (SLS1 to 3) to the different worlds: the astral world and lower and higher spirit world.
Compare with the notebook entry lower left of FMC00.339A on Rudolf Steiner's Gesamtausgabe (GA).
Lecture coverage and references
1922-10-09-GA218 The Experiences of Sleep and their Spiritual Background