Yoga Sutra I-44 ETAYAIVA SAVICARA NIRVICARA CA SUKSMA VISAYA VYAKHYATA - In the same way, savichara (reflective) and nirvichara (super or non-reflective) samadhis, which are practiced upon subtle objects, are explained.Yoga Sutra I-45 SUKSMA VISAYATVAM CALINGA PARYAVASANAM - The subtley of possible objects of concentration ends only at the undefinable.
On the two above sutras Swami Satchidananda comments on two other kinds of samadhis which are practiced similarly having finer elements for their objects. Satchiananda says basically "In other words, the finer objects [tanmatras, chittam and ego] ultimately end in the primal force called the Prakriti, or the primordial basic substance in its unmanifested condition." So basically in this condition there is no name, form or thought and just a fully balanced, tranquil unmanifested state of nature. And it is here that the mind has at he power to go to the very root of this unmanifested nature.
