A few technical notes:

3. The circuits of sun and moon were obvious choices for the calendar makers. Probably a solar calendar for the circuit of the year did not exist on Easter Island. Instead, the old concept was two 'years' - one 'year' when sun was 'present' and one 'year' when he was 'absent'.

"Hamiora Pio once spoke as follows to the writer: 'Friend! Let me tell of the offspring of Tangaroa-akiukiu, whose two daughters were Hine-raumati (the Summer Maid - personified form of summer) and Hine-takurua (the Winter Maid - personification of winter), both of whom where taken to wife by the sun ... Now, these women had different homes. Hine-takurua lived with her elder Tangaroa (a sea being - origin and personified form of fish). Her labours were connected with Tangaroa - that is, with fish. Hine-raumati dwelt on land, where she cultivated food products, and attended to the taking of game and forest products, all such things connected with Tane." (Best)

"The Sun spends part of the year with the Winter Maid in the south, afar out on the ocean. In the month of June occurs the changing of the Sun and he slowly returns to his other wife, to the Summer Maid who dwells on land and whose other name is Aroaro-a-manu. This period we call summer. And so acts the Sun in all the years. The child of the Summer Maid was Hikohiko. The old folk have told me [Hamiora Pio, a learned Maori] that at the time of the winter solstice the wise men of yore would say 'The Sun is returning to land to dwell with the Summer Maid.'

The word south in the first sentence should read north in order to make the statement consistent with the actual situation in the latitude of New Zealand. The myth had apparently been brought intact from an ancient habitat in the northern hemisphere." (Makemson)

4. The circuit of the sun around a 'year' (i.e. half-year) can be pictured as a circle, which at the same time then easily can be used to allude to the disc of the sun.

A circle is measured by its radius (or by its diameter). The circumference of the circle has a length equal to its diameter times π.

Counting glyphs in the text of E (Keiti) I reached 314, a number which I interpreted as 100π. Not many rongorongo tablets have all their glyphs still intact, but I could continue by identifying what seems to be the same number symbolism also in the texts of A and H:

However, it is not absolutely certain that the intention of the creators of these texts was (just) to document the numeric value of π. Furthermore, checking the numbers I discovered I had made a mistake: Although there are 628 glyphs in E there are 326 on side a and 302 on side b.