I think it's trying to say that all the aforementioned are pleasures of the flesh (of the body), and not so much intellectual stimulation; so the mind gets its pleasure by withdrawing into inner happiness.

I don't know what the author of this poem was on, but I'd sure like a large bottle of it!

Meanwhile the mind from pleasure less
Withdraws into its happiness;
The mind, that ocean where each kind
Does straight its own resemblance find;
Yet it creates, transcending these,
Far other worlds, and other seas;
Annihilating all that’s made
To a green thought in a green shade.

Whatever the pleasures the body can enjoy, the mind is still able to do much greater things - what it can do is transcend the reality, so all the luscious world described above is reduced to "a green thought in a green shade". The mind doesn't need any of this ("pleasure less") because it can create, improve upon the reality.

Perhaps this reformulation will help you, Stéphanie :-) As I read it, the mind is happy from the lack of mental stimulation and the (over) abundance of physical pleasures! Who needs mental pursuits when life is a bowl of cherries and you don’t even need to put out your arm to grab them. At the end of this poem, when the body is resting from all the pleasures that have been thrust upon it, the mind turns from a lot of pleasure (more pleasure) to happiness and contentment (less pleasure).

There is a play on words here that is going to be difficult to duplicate: pleasureless and pleasure less. The pleasures of the flesh have stopped, at least temporarily, while the speaker is resting upon the grass, but the pleasures are not all gone since there is the pleasure of happiness. In addition, there is problem of the rhyme that ‘less’ provided with ‘happiness.’ Another challenge for you! :-)

What a wondrous life is this that I lead!
Ripe apples drop around my head;
The luscious clusters of the vine
Do crush their wine upon my mouth;
The nectarine and curious peach do extend
themselves into my hands;
Stumbling over the melons as I pass by,
(and) trapped by flowers, I fall upon the grass.
And while all that is going on, the mind withdraws into happiness
from less pleasure.


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Note added at 1 hr (2007-08-13 17:09:42 GMT)
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I was typing up my explanation and had not seen Tony's answer when I wrote mine. As you can see, Tony and I are in agreement.

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Note added at 4 hrs (2007-08-13 20:33:38 GMT)
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A lovely thought, Stéphanie. I look forward to seeing the book some day soon :-)

I think there is an inversion within this sentence (Meanwhile the mind, from pleasure less,
Withdraws into its happiness.)it should be (Meanwhile the mind withdraws from pleasure less into its happiness)I.e it runs away from pleasure less depression frustration etc.. to something more pleasure