Citta (chit) is most important term in Upanishads, B. Gita, and Advaita Vedanta. SAME AS BUDDHISM. Proofs.

The Citta in the context of Vedantic doctrine
Buddhist doctrine in no way diverges
from these key doctrines as pertains the Nous, the Citta, the Will
THE UPANISHADS
ON THE CITTA
"(Cittam adhyatmam) the Citta is the sphere of the atman. What is
willed (cetayitavyam adhibhutam) is the sphere of the objective. The
Kshytriya (know of the field, i.e. Tathagata,
Buddha) is the divine principle." [Subala Up. 5.9]
"The subtle Atman is to be known as citta in which the fives senses
are centered. The whole of man's citta is pervaded by the senses (in
the common ignorant person). When the citta is
purified (visuddha citta = cittavumutta of Pali, or visuddha citta),
the Atman shines forth!" [Mundaka Up. 3.1.9]
"Verily all these (speech, thought, volition) have their center in
the citta" [Chand. Up. 7.5.2]
"(cittam atman) Citta is the Atman" [Chand. Up. 7.5.2]
"there is a city of eleven gates belonging to the upright citta. By
ruling it one doesn't grieve, is free" [Kath. Up. 2.2.1]
"whose citta is tranquil and attained to peace (samanvitaya,
Pali=samma'), let the sage teach in its very truth that gnosis about
Brahman by which one knows the Imperishable-person
(tattvato brahma-vidyam = Pali: Tathagata) of light." [Mundaka Up.
1.2.13]
"taking up that weapon the bow of the Upanishads, place in it the
arrow of samadhi. Draw the bow with the citta engaged in samadhi of
Brahman. Beloved, know that thy target (is gnosis
of) Brahman." [Mudaka Up. 2.2.3]
"He (Brahman spoken of as metaphorically and poetically as a god) is
the beginning, the (pre)source of all causes which unites (body and
soul). He is to be seen as beyond the three
periods of time, and without parts. After having worshiped that
resplendent god (Brahman, i.e. the Absolute) who is (source for) all
forms, the origin of being, (he) who abides in the citta."
[Svet. Up. 6.5]
"tranquility for the citta....One's own citta is the (source for)
samsara.....what a man wills (yac cittas tan-mayo bhavati) there he
becomes.....If a mans citta is so fixed upon Brahman, as
it as for any others to be fixed on the things of this world, who
then will NOT gain liberation?....the citta of him whose stains have
been washed away by samadhi and therein entered into
the atman cannot be described thru words." [Maitri Up. 6.34]


THE BHAGAVAD GITA
ON THE CITTA
"Having no desires with citta-atman (yatacittama, Pali: cittatta)
controlled.." [B.G. 4.21]
"Let the yogi perpetually keep the citta fixed in/upon the atman
(self-assimilation), alone, self-controlled free from all
desires." [B.G. 6.9]
"Serene and fearless, subdued in citta (samyamya maccitto = Pali
sammacitta) upon me (Brahman)." [B.G. 6.14]
"When the citta is established in the atman, liberated from desire,
therein he is in at peace." [B.G. 6.18]
"Like a flame in a windless place doesn't flicker to and fro, such is
a yogi subdued in citta is in union with the atman" [B.G. 6.19]
"Him in whom the citta is at rest, restrained by yoga (samadhi),
therein he beholds the atman, thru the self (citta) and rejoices in
the atman." [B.G. 6.20]
"If thou fixeth the citta upon me (Brahman), they reach me by
yoga." [B.G. 12.9]


SAMKARA ON
THE CITTA
"My citta, my true nature.." [Upadesa Sahasri 8.1]
""Just as one (fool) looks upon the body in the light of the sun as
having (in it) light, so too one looks (in error) at the reflection
(of the citta) mentation as having citta (light/Self) in it.
[Upadesa Sahasri 12.1]
"Just as bronzed poured into a mould assumes the shape of that mould,
so too the citta assumes and pervades (in ignorance) those sense
perceptions." [Upadesa Sahasri 14.3]
"The locus of memory is the citta" [Upadesa Sahasri 15.2]
"Gnosis is manifest in a pure citta, as if reflected in a clean
mirror" [Upadesa Sahasri 17.22]
"Just as the citta acquires a reflection of willing (cetana) and
appears to have willing in it, so too an image of a face in a mirror
appears to be a face, though it be mere illusion. [Upadesa
Sahasri 18.87]
"to say that the will is (equal to) willing (cittam cetanam) would
contradict the Vedas and reason. Moreover it would (falsely) imply
that the body is also the citta, as well as the other
senses (it has)." [Upadesa Sahasri 18.88](i.e. that the attribute of
will [citta] which is willing, is not will itself but its extrinsic
product)
"With the citta complete assimilated in the Supreme atman, Brahman,
the Absolute - then the world of appearances vanishes" [Vivekacudamani
398]
"The root of all feelings is in the citta. Merge the citta in the
Atman, the Supreme." [Vivekacudamani 407]
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