W Atop Hierophant's Tiara
It may be that the W of the Hierophant symbolizes the received Word which vivifies his ritual, blessing, prayer, and charity. It enters from Above to Below. So, here the W is the inspiring power of spiritual life, directly depicted from the Christian direction, while relevant to all inspired spiritual traditions. Thus, the placement of the W is far Above, at the zenith. It's almost as if looking down. (It's interesting that Paul Foster Case noticed and noted the W, letting it go in his revision of Waite's Hierophant design.) The W on the Grail cup may also be the Word, but the giving power of it, streaming down living waters of the Spirit to all that lies below, enlivening the lily pads. So the Hierophant receives and "channels" the power that the Grail cup outpours and provides. Of course, all this depends upon the W as standing for the Word, which may be only an aspect of the multiple meanings. This could all be unintentional synchronicity on the part of Waite and Smith, or it could be a conscious conjunction of the same symbol from two different but interrelated places.