Before him. The Chidah mentions it as an earlier tradition.
I’ll preempt Sam here by wondering why this is defferent from the Issur of Shoalin Bagoralos. Perhaps, because we are Mispallel that Hashem answer us through this method, and we only follow when it is a clear sign of Hashgacha, whereas Goralos would be deciding based on which side the oil flows.