Depends on how short. I for my part would recommend Shakespeare's sonnetts. Not too long, very emotional, there's lots of them, classic.

The economic anarchy of capitalist society as it exists today is, in my opinion, the real source of the evil. We see before us a huge community of producers the members of which are unceasingly striving to deprive each other of the fruits of their collective labour. I am convinced there is only one way to eliminate these grave evils, namely through the establishment of a socialist economy, accompanied by an educational system which would be oriented toward social goals.
~ Albert Einstein

Short ? yes, japanese haiku poetry achieved a high level concerning the writing of a poem..
In just three verses , an atmosphere of 'the minimal but essential' emerges...It has to do with a specific
'non abundant in meanings' culture, a sort of a Zen philosophy in literature..

Matsuo Bashō (1644–1694) is the best haiku writer in my opinion

Emily Dickinson may be. She has a lot of short poems.

And Omar Khayyam too. His quatrains are very famous.

Shakespeare..I never read but really famous writer here too..do you have any impressive
poem of him?

Haiku, yes..it is short one..however I don't know well about Haiku..you seems know well about it..do you read Haiku? Basho is really famous here...I know only the name..I was
studying the Buddhism so I'm interested in this fields..I didn't know about Zen philosophy in
literature..can you write more about it?

Emily Dickinson and Omar Khayyam..I didn't know..thanks for the recommendations.

@ Bianco
About Haiku poetry and its relation to Zen buddhism, this link could be a good start :

"Haiku and Zen"

Thanks for the good site.

You're welcome..

Try "A Shropshire Lad" by A E Housman. All the poems are short, and most of them are not hard to understand.

Aeschylus

Rectification :
Aeschylus was not a poet but an ancient greek theatrical drama writer - the founder of ancient greek tragedy maybe but never involved in poetry...

They are short and not hard to understand...it is good to me..thanks for recommendation..

I didn't know about Aeschylus. I'm interested in ancient greek things..do you have any good
greek poet?

@ Bianco
about ancient greek poets, I'd recommend Pindar and Sappho

Thanks for the recommendations..