When I translated the planetary prayers from the English translation of the Harleianus 5596 manuscript (Hygromanteia) by Marathakis into German for my personal use I stumbled over this peculiar expression in the prayer to Jupiter:
I conjure you, most valorous and most beneficial Jupiter, by the immeasurable ankle of god.
Marathakis seems to have been puzzled by this too as he added a footnote claiming that it must have been a corrupted text because he could not find any other reference to this 'ankle of god'.
Digging a bit around myself I came to a different conclusion. The Greek word for 'ankle' is αστράγαλος and the term might actually refer to a game of chance similar to dice popular in ancient Greece and elsewhere that was played with ankle bones:
Knucklebones (astragali), were an essential part of many ancient games: αστραγαλισμοσ was played using four astragali with different values on each side […] πευτελιξοι was played with five astragali, simultaneously thrown into the air to be caught on the back of the hand. Natural knucklebone was usually cut down, grinded, drilled and filled with lead. (source)
See also "Knucklebones"
I don't have access to an original Greek version of this prayer, so I can't fully verify if αστράγαλος was used, but if it was, then the expression would make more sense as god's 'game of dice' is immeasurable.