4. To describe what is unknown our own custom is denote it with X, but in ancient India the custom was to denote it with a zero symbol. Once upon a time zero stood for something not known, something which could not be described, not be given form, not be written down. The invention of a special symbol for the unknown was a great step forward for mankind, to give form to that which was without form, indeed which was nothing at all, which was 'empty', just a void.

The symbol 0 (or O) can be said to show the outline of something which cannot be seen, which is like the interior of an egg. Another, similar, idea is to draw a picture of a piece of cloth - a blanket - to indicate what is behind, not visible, not known. I think naos is a further such sign for what is not visible, not known:

'In Egyptology, naos refers to that which is hidden and unknown inside the inner sanctum of a temple, but also to little boxlike shrines, carried by statues etc.'

When the inside of an egg or a box (or the area behind a blanket) is to be visualized the obvious colour to use is pitch black. Light cannot be there. The 29th night of the Moon is therefore conventionally denoted by the sign · (just like the black hole in the ebony label of Pharaoh Hor-Den). The zero symbol used in India was consequently also a black 'zero', and for several reasons I would like to quote from a page in my glyph dictionary:

"The system of notation in the Bakhshali arithmetic [used in the Bakhshali manuscript written perhaps in the ninth century, but with contents composed 'no later than the fourth century AD'] is much the same as that employed in the arithmetical works of Brahmagupta and Bhaskara. There is, however, a very important exception. The sign for the negative quantity is a cross (+). It looks exactly like our modern sign for the positive quantity, but is placed after the number which it qualifies. Thus 

                      12                       7   +

                      1                         1

means 12 - 7 (i.e. 5). This is a sign which I have not met with in any other Indian arithmetic; nor, so far as I have been able to ascertain, is it now known in India at all. The sign now used is a dot placed over the number to which it refers. Here, therefore, there appears to be a mark of great antiquity.

The following statement, from the first example of the twenty-fifth sutra, affords a good example of the system of notation employed in the Bakhshali arithmetic:

                      l      1       1       1                                                                   

                      1       1       1       1    bha     32     phalam    108

                               3+     3+     3+ 

Here the initial dot is very much in the same way as we use the letter 'X' to denote the unknown quantity the value of which is sought. The number 1 under the dot is the sign of the whole (in this case, the unknown) number. A fraction is denoted by placing one number under the other without any line of separation; thus 

                      1

                      3

is 1/3, i.e. one-third. A mixed number is shown by placing the three numbers under one another; thus 

                      1

                      1

                      3

is 1 + 1/3 or 1 1/3, i.e. one and one-third. Hence 

                      1

                      1

                      3+ 

means 1 - 1/3 (i.e. 2/3). 

Multiplication is usually indicated by placing the numbers side by side; thus 

                      5                    32

                      8                    1      phalam     20 

means 5/8 * 32 = 20. Similarly 

                      1             1            1

                      1             1            1

                      3+           3+          3+ 

means 2/3 * 2/3 * 2/3 or (2/3)3, i.e. 8/27.  

Bha is an abbreviation of bhaga, 'part', and means that the number preceeding it is to be treated as a denominator. Hence 

                      1              1              1

                      1              1              1      bha

                      3+            3+            3+ 

means 1 : 8/27 or 27/8. The whole statement, therefore, means 27/8 * 32 = 108,  

                      l      1       1       1                                                                   

                      1       1       1       1    bha     32     phalam    108

                               3+     3+     3+ 

and may be thus explained - 'a certain number is found by dividing with 8/27 and multiplying with 32; that number is 108'."

The text is copied from Henrietta Midonick's The Treasury of Matemathics and she summarizes:

"The dot is also used for another purpose, namely as one of the ten fundamental figures of the decimal system of notation, or the zero (0 1 2 3 4 5 6 7 8 9). It is still so used in India for both purposes, to indicate the unknown quantity as well as the nought. With us the dot, or rather its substitute the circle (0), has only retained the latter of its two intents, being simply the zero figure, or 'the mark of position' in the decimal system.  

The Indian usage, however, seems to show how the zero arose, and that it arose in India. The Indian dot, unlike our modern zero, is not properly a numerical figure at all. It is simply a sign to indicate an empty place or a hiatus. This is clearly shown by its name sunya 'empty'."

The type of glyph which I thought needed the information from Midonick's book is rona:

rona
Rona

Figure made of wood, or stone, or painted, representing a bird, a birdman, a lizard, etc. Vanaga.

Drawing, traction. Pau.: ronarona, to pull one another about. Churchill.

While the rongorongo signs (rona) are generally 'carved out, incised' (motu), ta implies an incision ('cutting, beating') as well as the process of applying signs to the surface with the aid of a dye ... Barthel 2.

"After naming the topographical features of Easter Island with names from their land of origin, the emissaries went from the west coast up to the rim of the crater Rano Kau, where Kuukuu had started a yam plantation some time earlier.

After they had departed from Pu Pakakina they reached Vai Marama and met a man. Ira asked, 'How many are you?'

He answered, 'There are two of us.' Ira continued asking, 'Where is he (the other)?'

To that he answered, 'The one died.' Again Ira asked, 'Who has died?'

He replied, 'That was Te Ohiro A Te Runu.' Ira asked anew, 'And who are your?'

He answered, 'Nga Tavake A Te Rona.' (E:46)

After this, the emissaries and Nga Tavake went to the yam plantation." (Barthel 2)

"... RAP. rona means primarily 'sign' (an individual sign in the Rongorongo script or a painted or carved sign made on a firm background, such as a petroglyph), but also 'sculpture' (made from wood or stone, representing animals or hybrid creatures) ...

... rona (lona) implies the idea of 'maintaining a straight line' with ropes and nets and also the maintaining of a steady course (in MAO. and TUA.).

Te Rona is the name of a star in TUA., which Makemson (1941:251) derives from the mythical figure of 'Rona', who is connected with the moon and is considered to be the father of (the moon goddess) Hina (for this role in MAO., see Tregear 1891:423).

From west Polynesia come totally different meanings. Interesting perhaps is FIJ. lona, 'to wonder what one is to eat, fasting for the dead.' ..." (Barthel 2)

The Egyptian X, the region in the sky defined by the 4 stars Betelgeuze, Procyon, Phaet, and Naos, could indicate something unknown, not 'seen'. It is a region where the order of light so to say breaks down. The last of these 4 'pillars', Naos, can thus be regarded as the last part of the unknown, the inner sanctum, 'the box'.

I cannot resist illustrating my arguments with the boxlike 'coffin' towards the end of the journey in the flow from Chalchihuitzli (the Aztec version of Chalchiuhtilicue):

"... In Aztec mythology, Chalchiuhtlicue (also Chalciuhtlicue, or Chalcihuitlicue) ('She of the Jade Skirt') was the goddess of lakes and streams. She is also a patroness of birth and plays a part in Aztec baptisms. In the myth of the five suns, she had dominion over the fourth world, which was destroyed in a great flood. She also presides over the day 5 Serpent and the trecena [a 13-day period] of 1 Reed.

Her husband was Tlaloc and with him, she was the mother of Tecciztecatl and ruler over Tlalocan. In her aquatic aspect, she was known as Acuecucyoticihuati, goddess of oceans, rivers and any other running water, as well as the patron of women in labor. She was also said to be the wife of Xiuhtecuhtli. She is sometimes associated with a rain goddess, Matlalcueitl.

In art, Chalciuhtlicue was illustrated wearing a green skirt and with short black vertical lines on the lower part of her face. In some scenes babies may be seen in a stream of water issuing from her skirts. Sometimes she is symbolized by a river with a heavily laden prickly pear tree growing on one bank ..." (Wikipedia)

Xiuhtecuhtli (cfr at Atua Mata Viri) is another name for the Old Man who keeps the eternal fire at the bottom of the sea, alias Canopus.

I guess Chalchihuitzli, his wife, basically is the Milky Way. Another name for Chalchihuitzli was Chimalman - see at Adjuncts.