The most electric line in this chapter of the Targum Pseudo-Jonathan is hidden inside a description of a priestly accessory. On Exodus 28:30, the text explains what the Urim and Thummim actually were. Urim illuminate their words, and manifest the hidden things of the house of Israel. Thummim fulfil their work to the high priest, who seeketh instruction by them before the Lord.
Then the Targum delivers the secret. In these objects is engraven and expressed the Great and Holy Name by which were created the three hundred and ten worlds — the hidden worlds reserved, the Sages taught, as reward for the righteous. That same Name was engraven and expressed in the foundation stone wherewith the Lord of the world sealed up the mouth of the great deep at the beginning.
The geography is breathtaking. The Foundation Stone beneath the Holy of Holies, sealing the primordial waters. The Urim and Thummim on the high priest's chest, carrying the same Name. The hidden letters link the top of the sanctuary to the bottom of the world. When the high priest asked a question, he was not consulting an oracle. He was holding the very seal that kept chaos from returning.
The promise that follows is bold. Whosoever remembereth that holy name in the hour of necessity shall be delivered. The takeaway for the rest of us, who will never wear the breastplate, is that the Name is not locked in the Temple. It is available to memory, and memory is available to anyone.