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