What kind of mental state does the meditation on four elements generate?

I don't know but maybe this passage about a skilled butcher from chapter III of the Book of Zhuang Zi is a clue.

Prince Hui's cook was cutting up a bullock. Every blow of his hand, every heave of his shoulders, every tread of his foot, every thrust of his knee, every whshh of rent flesh, every chhk of the chopper, was in perfect harmony,—rhythmical like the dance of the Mulberry Grove, simultaneous like the chords of the Ching Shou.

"Well done!" cried the Prince. "Yours is skill indeed."

"Sire," replied the cook; "I have always devoted myself to Tao. It is better than skill. When I first began to cut up bullocks, I saw before me simply whole bullocks. After three years' practice, I saw no more whole animals.

And now I work with my mind and not with my eye. When my senses bid me stop, but my mind urges me on, I fall back upon eternal principles. I follow such openings or cavities as there may be, according to the natural constitution of the animal. I do not attempt to cut through joints: still less through large bones.

"A good cook changes his chopper once a year,—because he cuts. An ordinary cook, once a month,—because he hacks. But I have had this chopper nineteen years, and although I have cut up many thousand bullocks, its edge is as if fresh from the whetstone. For at the joints there are always interstices, and the edge of a chopper being without thickness, it remains only to insert that which is without thickness into such an interstice.

By these means the interstice will be enlarged, and the blade will find plenty of room. It is thus that I have kept my chopper for nineteen years as though fresh from the whetstone.

"Nevertheless, when I come upon a hard part where the blade meets with a difficulty, I am all caution. I fix my eye on it. I stay my hand, and gently apply my blade, until with a hwah the part yields like earth crumbling to the ground. Then I take out my chopper, and stand up, and look around, and pause, until with an air of triumph I wipe my chopper and put it carefully away."

"Bravo!" cried the Prince. "From the words of this cook I have learnt how to take care of my life."

Since the elements are really expressing states i.e. water is not really water but liquid, wetness, changing, the idea is perhaps about the composition (and decomposition) of bodies. Individual bodies like yours and mine but also the larger structures we belong to: our families, our nations, the international community etc., which also function like bodies, where different people playing different roles and where mind work is at the top and support work is at the base. In starvation, the human body will take food from itself to feed the brain and keep it going and will only take from parts of the brain to feed the most important parts of the brain when it has no choice. And what is an ox/bullock in the ancient world? The source of work/energy. Hence harnessing/yoking and the plough.

If you read the section on the contemplation on the body, there is a sequence:

1. Breathing and breathing patterns
2. Postures of the body
3. Full awareness of bodily actions
4. Body made up of internal organs
5. Body made up of elements
6. Decomposition at death
7. Dead body eaten by animals
8. Skeleton with flesh and blood
9. Skeleton without flesh and blood
10. Skeleton alone
11. Bones strewn about

And so on.

Based on this, the contemplation on the body being composed of the four elements is part of the overall contemplation that the body is a sankhara (compounded and/or conditioned thing), and this leads to the insight that anicca (impermanence), dukkha (suffering) and anatta (not-self) applies to it.

The standard statement in the sutta from Thanissaro Bhikkhu's translation here:

"In this way he remains focused internally on the body in & of itself, or externally on the body in & of itself, or both internally & externally on the body in & of itself. Or he remains focused on the phenomenon of origination with regard to the body, on the phenomenon of passing away with regard to the body, or on the phenomenon of origination & passing away with regard to the body. Or his mindfulness that 'There is a body' is maintained to the extent of knowledge & remembrance. And he remains independent, unsustained by (not clinging to) anything in the world. This is how a monk remains focused on the body in & of itself.

So, the insight into the impermanence, suffering and not-self of the compounded and conditioned thing, that is the body, leads to the monk becoming independent and not clinging to anything in the world.

In the Tibetan tradition, there are space, air, fire, water and earth, and are understood as the underlying energies from which the physical world, our bodies, our emotions, and our minds arise. The elements are addressed in all nine levels of teachings of Bön, including shamanism, tantra and Dzogchen.

The five Platonic solids were assigned to elements by Plato in the Timaeus 56b, 55d— fire (tetrahedron), earth (cube), air (octahedron), water (icosahedron), ether (dodecahedron). "To earth, let us assign the cubic form, for earth is the most immovable of the four and the most stable of all bodies... the pyramid is the solid which is the original element and seed of fire, and let us assign the element which was next in the order of generation to air, and the third to water.

In yoga all elements can be produced from joining of male and female energies in different chakras of the body.To produce fire we join in the solar plexus male and female energies,this not only produces heat but also bliss.

However all elements are impermanent,once you clean each one you gain the notion of emptiness and both your body and your mind become pure,just like Milarepa you won't feel the cold of the winter or the heat of the summer!

Thereafter, over time, the sense of identification with the four elements loosens and is seen through.All happens spontaneously!

Now the yoga has completed its aims: Impermanence has been realised and I think this is clever butcher's point of view!