They were a whole genre of poems called "adhama kavyas." Literally, in Sanskrit, it means 'inferior poems'. Here's a nice (though a little flowery) exposition on these: https://www.dropbox.com/s/swivmkyr138wd01/14339015-The-wonde...

They were deemed inferior because they were low on traditional poetic quality- meaning, prosody, and language, and high on a sort of acrobatics.

There are fascinating poems, including palindromes, meaningful poems written by repeating the same letter, nested structures, etc.