I have a reference for you:
Meditation and the Bible by Aryeh Kaplan 1992 (3rd ed.) Samuel Wiser Inc. York Beach Maine
It's a pretty comprehensive text. I also find Gershom Scholem's Major Trends in Jewish Mysticism has some chapters which address the topic.
I'm interested in all forms of meditation and especially how eastern philosophy interfaces with Jewish Mysticism. If interested e-mail me: dctrzphd@aol.com Good luck in your searchings.