Samadhi is of two kinds: one turned outward, one turned inward. The outward-turned consciousness is always first. You are in the stage of Samadhi belonging to the outward-turned waking consciousness, when you can pass beyond the objects to the principles which those objects manifest, when through the form you catch a glimpse of the life. Darwin was in this stage when he glimpsed the truth of evolution. That is the outward-turned Samadhi of the physical body.
This is technically the Samprajnata Samadhi, the “Samadhi with consciousness,” but to be better regarded, I think, as with consciousness outward-turned, i.e. conscious of objects. When the object disappears, that is, when consciousness draws itself away from the sheath by which those objects are seen, then comes the Asamprajnata Samadhi; called the “Samadhi without consciousness”. I prefer to call it the inward-turned consciousness, as it is by turning away from the outer that this stage is reached.
These two stages of Samadhi follow each other on every plane; the intense concentration on objects in the first stage, and the piercing thereby through the outer form to the underlying principle, are followed by the turning away of the consciousness from the sheath which has served its purpose, and its withdrawal into itself, i.e., into a sheath not yet recognised as a sheath.
It is then for a while conscious only of itself and not of the outer world. Then comes the “cloud,” the dawning sense again of an outer, a dim sensing of “something” other than itself; that again is followed by the functioning of the nigher sheath and the Recognition of the objects of the next higher plane, corresponding to that sheath. Hence the complete cycle is:
Samprajnata Samadhi, Asamprajnata Samadhi, Megha (cloud), and then the Samprajnata Samadhi of the next plane, and so on.
Taken From “An Introduction To Yoga” by Annie Besant