(perhaps related to Sanskrit krtsna, 'all, complete, whole'), is the name for a purely external device to produce and develop concentration of mind and attain the 4 absorptions (jhāna q.v.).
It consists in concentrating one's full and undivided attention on one visible object as preparatory image (parikamma-nimitta), e.g. a colored spot or disc, or a piece of earth, or a pond at some distance, etc., until at last one perceives, even with the eyes closed, a mental reflex, the acquired image (uggaha-nimitta). Now, while continuing to direct one's attention to this image, there may arise the spotless and immovable counter-image (patibhāga-nimitta), and together with it the neighbourhood-concentration (upacāra-samādhi) will have been reached. While still persevering in the concentration on the object, one finally will reach a state of mind where all sense-activity is suspended, where there is no more seeing and hearing, no more perception of bodily impression and feeling, i.e. the state of the 1st mental absorption (jhāna, q.v.).
The 10 kasinas mentioned in the Suttas are: earth-kasina, water, fire, wind, blue, yellow, red, white, space, and consciousness. "There are 10 kasina-spheres: someone sees the earth kasina, above, below, on all sides, undivided, unbounded .... someone see the water-kasina, above, below, etc." (M. 77; D. 33) Cf. abhibhāyatan, bhāvanā; further s. Fund. IV.
For space and consciousness-kasina we find in Vis.M. V the names limited space-kasina (paricchinnākāsa-kasina; . . . s. App. ) and light-kasina (āloka-kasina).
For full description see Vis.M. IV-V; also Atthasālini Tr. I, 248.