A kind of Utkālika Śruta (a category of Āgamas (canonical works), which is allowed to be studied at all time barring the akāla prahara (i.e., the period in which the study of Āgamas is prohibited));
in this treatise, there is an elaborate exposition on Dhyāna (meditation), including the description of its types and sub-types...
thiramajjhavasāṇaṃ jhāṇaṃ, vibhayaṇaṃ vibhattī sabhedāṃ jhāṇaṃ jattha vaṇṇijjati ajjhayaṇe tamajjhayaṇaṃ jhāṇavibhattī.
(Nandī 77 Cū p. 58)