Siman 152

(2.) In the aforementioned year 5566, when he began to speak with me about the rectification of the souls he is occupied with — which is the matter of the Master of the Field etc. as mentioned above — he then said to me: "In Zlatipoleye, a little of this became known to me" — that there he began to know something of this matter of the Master of the Field. And it is understood from his words that there he began to know something, and the main knowing is now. And he said that Rabbi Shimon bar Yochai alluded to a little of this in the holy Zohar [Shemos 166b]. And what was understood from his words was: that in the matter of this Master of the Field, as he now knows it, no tzaddik in the world yet knew it.