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 & uniform
object or aspect...
There are 10 objects. Consciousness itself
taken as entirety 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 heap 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 called the 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
Yves Klein blue
is the
mental reflex-image (patibhāga-nimitta) and linked 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. Neither can any
ill-will (vyāpāda) irritate the mind. So is also
all lethargy & laziness (thīna-middha) overcome.
Neither can any restlessness or regret (uddhacca-kukkucca) or wavering in confused doubt
(vicikicchā) divert or distract
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 and 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 & void of all thinking & pondering...
When the joy
fades away the third jhāna is reached, which is characterized by
a sweet serene
equanimous happiness (upekkhā-sukha). At stilling this
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, pliable,
devoid of noise, completely
able to act,
rock-solid, 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:
https://what-buddha-said.net/library/pdfs/PathofPurification2011.pdf

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

The Jhānas in Theravada
Buddhist Meditation by Henepola Gunaratana Mahathera:
https://what-buddha-said.net/library/Wheels/wh351.pdf