Some references from Beer's "Encyclopedia of Tibetan Symbols and Motifs":
A single-pointed vajra represents both the central chan-
nel as Mt Meru's central axis, and the union of all duality
symbols conceived of as non-dual. These include wisdom and
compassion, emptiness and bliss, absolute and relative truths.
The deity Kalachakra is described as wearing a long rosary of
single-pointed vajras, although iconographically Kala-
chakra's rosary is more often depicted as a long chain of
five-pronged vajras with a crossed vajra at its lower centre.
The sharp point of Yamantaka's harpoon- which is de-
scribed as a single-pointed vajra - symbolises penetrative
The thousands of lines of the Prajnaparamita can be summed up in the following two sentences:
1) One should become a Bodhisattva (or, Buddha-to-be), i.e. one who is content with nothing less than all-knowledge attained through the perfection of wisdom for the sake of all beings.
2) There is no such thing as a Bodhisattva, or as all-knowledge, or as a ‘being’, or as the perfection of wisdom, or as an attainment.
To accept both these contradictory facts is to be perfect. - Conze