Friends:

Absorption is inducible by Object Unification!

Kasina means: Entirety, Totality, Unity, Wholeness and Oneness...
It is a purely external method of inducing concentration and reach
jhāna absorption by unifying & condensing all undivided attention
on a single homogenous, pure and uniform object or aspect...
There are 10 objects. Consciousness itself is regarded the finest:
1: The Earth kasina, 2: Water kasina, 3: Fire kasina, 4: Wind kasina,
5: The Blue kasina, 6: Yellow kasina, 7: Red kasina, 8: White kasina,
9: The Light or the consciousness kasina, 10: The Space kasina.
The colour kasinas is a blue, yellow, red or white circular disk ~1"
feet in diameter of cloth, or painted cardboard or plywood, which
is set up ~2 meters from the meditator who by gazing intensively at
it internalizes it and thereby construct an artificial visualization!
In the earth kasina, the object of gazing may be a ploughed field
seen from afar, or a round piece of earth prepared for the purpose.
In the water kasina one may gaze at a pond seen from an elevation,
or at water contained in a vessel. Similarly with the fire and wind.
One must keep the mind away from all outside contacts & various
thoughts on other objects, as well as all those disturbing and often
detrimental mental visions or pseudo-hallucinations that may arise.
Now, while exclusively fixing the eyes and thoughts on the blue disk
as the sole object, the things around the disk seem to disappear and
the disk itself becomes more and more a purely mental appearance.
Then, whether the eyes are opened or closed, one perceives this now
purely mentalized kasina disk, as wholly pure uniformly bright blue.
This is the so-called acquired image (uggaha-nimitta) which, though
apparently induced by means of the physical eyes, is nevertheless
produced and visualized only by the mind, independent of the eyes!
This fragile mentally produced image one should make so steady it
no longer vanishes, but remains firmly fixed in the mind. Then it will
become continually steadier, brighter, and more intensive. Such all
pervading pure blue is the mental reflex-image (patibhāga-nimitta)
& associated with it is the access concentration (upacāra-samādhi).
During this stage all mental hindrances (nīvarana) have temporarily,
been suppressed.  No sensual lust (kāma-chanda) can arise in such
focused state. No ill-will (vyāpāda) can irritate the mind. So is also
all lethargy and laziness (thīna-middha) overcome. No restlessness
or regret (uddhacca-kukkucca) and no wavering in confused doubt
(vicikicchā) can any more divert the mind. If it is still possible for
these five mental hindrances to arise, there can be no lasting calm
of the mind. When they are gone, & the calm appears is if even solid
one may reach the absorption level concentration (appanā-samādhi)
and thereby enter into the first jhāna. The first jhāna is a state of
calm peace, joyful bliss, and directed thought & sustained thinking
(vitakka-vicāra), i.e. inner speech or verbal activities of the mind...
By the fading away & stilling of these verbal activities of the mind,
one has attained the second jhāna, a state of calm joy & happiness
(piti-sukha), freed from all thinking and pondering. When the joy
fades away the third jhāna is reached,  which is characterized by
a serene equanimous happiness (upekkhā-sukha). At the ceasing of
happiness, a state of perfect equanimity (upekkhā) remains. This is
called the fourth jhāna. After emerging from the fourth jhāna, the
mind becomes serene, pure, lucid, stainless, devoid of wrong, pliable,
able to act, firm and imperturbable. Such mind is capable of all...

 

The Blessed Buddha explained:
Monks, there are the ten kasina devices (for concentration).
What are the ten? Someone perceives the earth kasina, above, below,
on all sides, undivided, unbounded; another person perceives the water
kasina... the fire kasina... the wind kasina... the blue... yellow... white...
red kasina... the space kasina... the consciousness kasina, above, below,
on all sides, undivided, unbounded. These are the ten kasina devices.
Among these ten, this is the highest — when one perceives this subtle
consciousness kasina above, below... unbounded. There are, indeed,
monks, such persons who perceive in that way. But even for persons
who thus perceive, change takes place, transformation takes place!

For a detailed explanation of the kasina exercises see Vism IV, V.
The Path of Purification: Visuddhimagga. Excellent translation by
Bhikkhu Nanamoli. Written by 'the great explainer' Buddhaghosa
in 5th century AC on Ceylon:
http://www.pariyatti.com/book.cgi?prod_id=771100

More on Mental Absorption (Jhāna):
http://What-Buddha-Said.net/drops/Requisites_for_Jhana_Absorption.htm
http://What-Buddha-Said.net/drops/III/The_Concentration_Ability.htm
http://What-Buddha-Said.net/drops/II/The_5_Mental_Hindrances.htm
http://What-Buddha-Said.net/drops/III/Concentration_Samadhi.htm
http://What-Buddha-Said.net/drops/III/Feeding_Concentration.htm
http://What-Buddha-Said.net/drops/Samma-Samadhi.htm