What is wisdom? How to contemplate?
Many people will disagree with my answer because they wish to believe they are practising cittanupassana.
The word &quot;anupassana&quot; means to &quot;watch closely&quot; therefore cittanupassana is not &quot;noting&quot; because noting is thinking rather than watching.
Also, because &quot;anupassana&quot; means to &quot;watch closely&quot;, there is no thinking whatsoever in the mind when cittanupassana occurs.
For example, in the practise of Anapanasati, cittanupassana is practised with full concentration, i.e., with knowing each in-breath &amp; each out-breath.
About cittanupassana in Anapanasati, the Buddha commented:

I do not say that there is the development of mindfulness of breathing for one who is forgetful, who is not fully aware.
MN 118

Cittanupassana occurs after the breathing has calmed &amp; after the rapture that arises from calming breathing is also calmed.
Cittanupassana is directly knowing the quality &amp; purity of the mind. Although during cittanupassana the mind can have stains of greed, hatred &amp; delusions, these stains are not thoughts or thinking. They are the energy or mood of the stains/defilements themselves. Therefore, MN 10 says:

And how, monks, does a monk fare along contemplating mind in the mind?
Herein, monks, a monk knows intuitively the mind with attachment as a
mind with attachment;
he knows intuitively the mind without attachment, as a mind without
attachment;
he knows intuitively the mind with hatred, as a mind with hatred;
he knows intuitively the mind without hatred, as a mind without
hatred;
he knows intuitively the mind with confusion, as a mind with
confusion;
he knows intuitively the mind without confusion, as a mind without
confusion;
he knows intuitively the mind that is contracted, as a mind that is
contracted;
he knows intuitively the mind that is distracted, as a mind that is
distracted;
he knows intuitively the mind that has become great, as a mind that
has become great;
he knows intuitively the mind that has not become great, as a mind
that has not become great;
he knows intuitively the mind with (some other mental state) superior
to it, as a mind with (some other mental state) superior to it;
he knows intuitively the mind with no (other mental state) superior to
it, as a mind with no (other mental state) superior to it;
he knows intuitively the mind that is composed, as a mind that is
composed;
he knows intuitively the mind that is not composed, as a mind that is
not composed;
he knows intuitively the mind that is freed, as a mind that is freed;
he knows intuitively the mind that is not freed, as a mind that is not
freed.
MN 10