Kasina: 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 Jhanas. 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 contact and feeling, i.e. the state of the 1st mental absorption.
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.. see: App. and light-kasina āloka-kasina
For full description see Vis.M IV-V
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.