On the nature of things (books 1 - 3)   

And through the frame is stirred by nothing new.
But when the mind is moved by shock more fierce,
We mark the whole soul suffering all at once
Along man's members: sweats and pallors spread
Over the body, and the tongue is broken,
And fails the voice away, and ring the ears,
Mists blind the eyeballs, and the joints collapse,-
Aye, men drop dead from terror of the mind.
Hence, whoso will can readily remark
That soul conjoined is with mind, and, when
'Tis strook by influence of the mind, forthwith
In turn it hits and drives the body too.

And this same argument establisheth
That nature of mind and soul corporeal is:
For when 'tis seen to drive the members on,
To snatch from sleep the body, and to change
The countenance, and the whole state of man
To rule and turn,- what yet could never be
Sans contact, and sans body contact fails-
Must we not grant that mind and soul consist
Of a corporeal nature?- And besides
Thou markst that likewise with this body of ours
Suffers the mind and with our body feels.
If the dire speed of spear that cleaves the bones
And bares the inner thews hits not the life,
Yet follows a fainting and a foul collapse,
And, on the ground, dazed tumult in the mind,
And whiles a wavering will to rise afoot.
So nature of mind must be corporeal, since
From stroke and spear corporeal 'tis in throes.
Now, of what body, what components formed
Is this same mind I will go on to tell.
First, I aver, 'tis superfine, composed
Of tiniest particles- that such the fact
Thou canst perceive, if thou attend, from this:
Nothing is seen to happen with such speed
As what the mind proposes and begins;
Therefore the same bestirs itself more swiftly
Than aught whose nature's palpable to eyes.
But what's so agile must of seeds consist
Most round, most tiny, that they may be moved,
When hit by impulse slight. So water moves,
In waves along, at impulse just the least-
Being create of little shapes that roll;
But, contrariwise, the quality of honey
More stable is, its liquids more inert,
More tardy its flow; for all its stock of matter
Cleaves more together, since, indeed, 'tis made
Of atoms not so smooth, so fine, and round.
For the light breeze that hovers yet can blow
High heaps of poppy-seed away for thee
Downward from off the top; but, contrariwise,
A pile of stones or spiny ears of wheat
It can't at all. Thus, in so far as bodies
Are small and smooth, is their mobility;
But, contrariwise, the heavier and more rough,
The more immovable they prove. Now, then,
Since nature of mind is movable so much,
Consist it must of seeds exceeding small
And smooth and round. Which fact once known to thee,
Good friend, will serve thee opportune in else.
This also shows the nature of the same,
How nice its texture, in how small a space