Here’s a poem from 1860. I found it at About.com (great site for language lovers). This shows that writers were playing with language long before text messaging made it fashionable.

Essay to Miss Catharine Jay

An S A now I mean 2 write
2 U sweet K T J,
The girl without a ||,
The belle of U T K.

I 1 der if U got that 1
I wrote 2 U B 4
I sailed in the R K D A,
And sent by L N Moore. . . .

This S A, until U I C
I pray U 2 X Q’s
And do not burn in F E G
My young and wayward muse.

Now fare U well, dear K T J,
I trust that U R true–
When this U C, then you can say,
An S A I O U.
(Charles Carroll Bombaugh, Gleanings From the Harvest-Fields of Literature, Science and Art: A Melange of Excerpta, Curious, Humorous, and Instructive, 2nd ed. Baltimore: T. Newton Kurtz, 1860)