This river starts in Eden, then flows out of Eden to water the garden. This implies a water that exists both in the Holy of Holies and also in the Hekal, split by the veil, which is what Moses 2 also tells us. Somehow, the waters of the Holy of Holies were fourfold, corresponding to the four directions (and the four cherubim?).
We're told the names of the rivers and the lands to which they flow. Also, we hear that the river Hiddekel flows east, and the Pison "compasseth" (surrounds) Havilah, where there are gold, bdellium, and onyx. "Havilah" is strikingly reminiscent of "Eve" in Hebrew: CH-V-I-L-H and CH-V-H. Did the river Pison surround the tree of life in the land of Eve? The temple furnishings, including the ark, are gold; bdellium is a myrrh-like spice, but the only other mention of it in the Bible is in a comparison to manna, a pot of which was kept in the ark; the high priest wore two onyx stones in his breastplate.
It's hard to escape the conclusion that the river Pison encompassed the Holy of Holies.