You can raise stat + potentials in 1.2.0pre7 using herbs using the following method:

-Raise your To/Dx/Wi with herbs to 1 point below potential maximum, say, 11 (12 max).
-Eat/use a very large pile of morgia roots/moss. 20 minimum, I would recommend.
-Wait a large number of turns. Your To/Wi/Dx will increase as normal. If you are lucky you should have enough leftover training to raise your potential as well. Now you are at 12 (13). Repeat as necessary.

Basically, if you significantly overtrain a stat, you can still get potential increases from the overflow through herbs even though you can't get potential increases normally.