What does "even that" mean

i was reading this ancient Egyptian proverb the other day and found it hard to understand because the words "even that" seemed to throw me off. I couldn’t really grasp the message the writer was trying to convey. well here it is. If you can explain what "even that" means in this context.

Well here is the quote:

The blessings of thy eternal part are health, vigor, and proportion. The greatest of these is health. What health is to the body, even that is honesty to the soul.