He used a charitable trust to do it in a way that maximized the gift and provided him an income for life.

The coolest thing about his story is that his generosity was coupled with a genuine contentment and focus on simplicity.

In the words of the apostle, Paul:

"I have learned to be content in whatever circumstances I am.  I know how to get along with humble means and I also know how to live in prosperity.  I can do all things through him who strengthens me."

-- Philippians 4:11-13