Having just written a "part one" about the terminal stones of its southern kerb, that is only one of many "features in the making", but , with monuments, I have recently been driven by radii in recent weeks.
So that locates a lunar fathom. At Le Manio there were clearly two day-inch counts, one for three solar years and another for four years. Four years is a convenient length since an extra whole day is resolved to make 1461 days over four years. But equally, it could also have been (or also been been used as) a single solar year using four inches per day, as per the lunar fathom. The beauty of that fathom is its capacity to count days whilst maintaining a natural fathom-count, of lunar months. If so the excess of solar year over lunar year would be 4 x 10.875 inches. Strangely, when Robin and I were surveying Le Manio in 2010, we made a four-square structure at the end of the southern kerb - which is where the "four-year" count would have arced down, like the three-year count (see below). A small stone is set beyond the three year count to likely signify the end of the four year count.
Four square shape placed at end of southern kerb
In looking through photos from 2010 much suppressed work can be seen, some integrating the three and four year counts through an intermediary three square representing the length of three eclipse years on the southern kerb (see below).
Three eclipse years then end on the lateral stone 35 seen here:
This means that the FORM of the monument (the subject of the part 2 to come) had, as part of its purpose, the ability to derive the length of the eclipse year geometrically using multiple squares. This explains why the monument is the shape it is whilst we already know that its angle is such as to enable the symbolic counting of years towards the midsummer sunrise point of Carnac in 4000 BCE. In part two can come the explanation as to how the southern kerbs alignment can be also (amazingly) be significant in itself, an angle greater than that of a 5-12-13 triangle.
Returning to the "four year count" as being one year counted four inches per day, each month would then be 118.125 inches long, that is the "lunar fathom", less by 1/64th part than the double fathom of ten feet. This desire to quadruple the count has enabled a single month to be defined using eighths of an inch rather than 32nds of an inch. It is this sort of concern about allowing only a numeracy possible to the megalithic, without mathematics but with metriology and geometry, that it can become credible that an advanced astronomy was thereby possible to the late Stone Age.