The weekday (Sunday-Friday) and Shabbat (Saturday) Siddur follow the format of The Ari, Rav Isaac Luria, foremost rabbi and Kabbalist sage from the 15th century, considered by many to be the father of contemporary Kabbalah. Both Siddurs include Kabbalistic kavanot (intentions) and meditations from the Ari, the Zohar and the Ramchal (Moshe Chaim Luzzatto).