The White Lights ~ 2006
There is a metaphoric connection and quite literal connection. They overlap. Any TOR could be considered the Holy Grail. The Holy Grail exists in the physical and it also exists in the spiritual in the sense that one can achieve those benefits by reaching a certain state of mind and heart and well being and of action and rejuvenation.
In biblical terms and later the Holy Grail was talked about. It was referred to in several different ways, one of them being the Cup of Christ, but it was also referred to as the spiritual aspects and also the physical aspects. Over the centuries it began to be referred as a sort of generic thing to mean very many different things. But the in original intention of it there is a direct parallel.