How to turn off TOAST on a table/column

I am looking into some performance issues with an application I have.  I 
want to do some testing to see how much overhead TOAST adds to my 
application.  I have a table that performs a similar function to the 
pg_largeobject table.  I have noticed that pg_largeobject doesn't have 
toast enabled (i.e. reltoastrelid is 0).  However when I create my table 
it always gets a value for reltoastrelid.  Since pg_largeobject is 
created without toast, I am assuming this is intentional and that for 
certain classes of tables it may make sense not to toast the tuples. 
Which makes sense because inserting into the toast table will involve 
extra disk IOs and if the tuple would have fit into the base table these 
extra IOs could be avoided.

So how do I create a table without toast enabled?  I have looked through 
the docs for 'create table' and didn't see anything that indicates this 
is possible.  Is there some undocumented syntax?

thanks,
--Barry