Here's how a snowflake is a table and a O is an unfamiliar notion.  From A Handbook of Phrenotypics for Teachers and Students by Major Beniowski, 1842.

Here's someone who somehow managed to take 30 years to come up with a symbol for the word "the," only to gain the general public's indifference.  From Popular Mechanics, 1929.

From Pure Logic by William Stanley Jevons, 1864.  The text reads, "Let it be borne in mind that the letters A, B, C, &c., as well as the marks +, 0, and =, afterwards to be introduced, are in no way mysterious symbols."  However, we found some rather mysterious meanings of A, B, C for our One-Letter Words: A Dictionary, and some even more mysterious meanings of &c for our book entitled Ampersand.

An entire chapter of type symbols, from Judy, Or The London Serio-Comic Journal, 1869.

"He made a big 'O' with two little crosses in the middle."  From "The Double X Mystery" by Thomas Keyworth, in Cassell's, 1890.

"An immense 'O' was seen upon it, with two 'X's' inside."   From "The Double X Mystery" by Thomas Keyworth, in Cassell's, 1890.

"Pause — a dot in a semicircle."  From "Musical Gestures," Cassell's, 1894.

Here are some uncanny mystical ciphers from Zanoni by Edward Bulwer Lytton, 1856.

The Codex Vaticanus explains that these ancient Mexican symbols are the twenty figures that rule over men [deer or stag, wind, rose, earthquake, eagle, vulture, water, house, skull or death, rain, dog, rabbit, flint, air, monkey, cane, grass or herb, lizard, tiger, and serpent] and that cure in a corresponding manner those who become ill or suffer pains in any part of the body.  "The sign of the wind is assigned to the liver; the rose to the breast; the earthquake to the tongue; the eagle to the right arm; the vulture to the right ear; the rabbit to the left ear; the flint to the teeth; the air to the breath; the monkey to the left arm; the cane to the heart; the herb to the bowels; the lizard to the womb of women; the tiger to the left foot; the serpent to the male organ of generation, as that from which their diseases proceed in their commencement; for in this manner they consider the serpent, wherever it occurs, as the most ominous of all their signs."  From the Annual Report of the Bureau of Ethnology, 1889.

Riding a silcrow, from Die Muskete, 1912.

This is the symbol left in the crib after the Lindbergh baby was famously taken away.  "There has been no genuinely convincing analytic work done on [this symbol] with respect to the Lindberg story" (Jerry Kroth, The Lindbergh Kidnapping, 2011).  [Note that the three black rectangles are actually holes that were punched in the paper and are not technically part of the design.]  The shaded object in the center is, of course, the "black egg" of alchemy, symbolizing the nigredo (a stage of putrefaction; the final step toward the "philosopher's stone" of enlightenment) and expressing "the precarious balance of the hermaphrodite, exalted by a [threatened] equilibrium" (Johannes Fabricius, Alchemy: The Medieval Alchemists and Their Royal Art, 1994).

The General Dynamics 1964 Mercury Program and time capsule (to be opened in year 2464).  Here's the artist's rendering and the monument being fashioned.

"Tse'-xo-be (Spider), life symbol of the Osage tribe's Hon-ga (sacred person) U-ta-non-dsi (isolated one) Gens (the earth)."  From the Annual Report of the Bureau of American Ethnology to the Secretary of the Smithsonian Institution, 1915.

The symbolism here is rather blatant — the rooster is the male principle who engendered a newborn spool of cotton thread.  As someone once said, "Wool makes yarn; flax makes linen; cotton makes cotton."  From c. 1890.

Years ago we developed a calendar system that tracks the flow and relationships of telltale words and symbols.  One can generate an entire month's calendar to test its accuracy in predicting events in daily life.  The link is http://mysteryarts.com/magic/calendar/.