Indian Yellow

Indian yellow is yellow pigment used in watercolor and oil paintings. The pigment, manufactured in rural India, was made from the dried urine of the cows that were fed only on mango leaves [1]. Since the cows were extremely undernourished, the process was declared outlaw in 1908 and the pigment has not been available commercially since 1921.

This made the pigment the rarest color of the pigment collection at the Harvard Art Museum, Cambridge [2].

Example of use [3]

Vincent van Gogh, The Starry Night, 1889


Indian yellow was employed together with Indian yellow for deeper yellow of the moon and the stars.



[1] Artists’ Pigments: A Handbook of Their History and Characteristics, Volume 1 Available at

[2] A Great Big Story’s video: A Vault of Color: Protecting the World’s Rarest Pigments


Eidetic Memory

Eidetic memory, sometimes called photographic memory or total recall, is an ability to recall images, sounds, or objects in memory with great precision and is not acquired through mnemonics.

A person with the ability is called an eideticker.

An example of a notable eideticker is the mathematician John von Neumann.


Tupper’s Self-Referential Formula

Imagine a graph of a formula that actually contains your name in it.

It’s this so-called Tupper’s self-referential formula

\displaystyle\frac{1}{2} < \left\lfloor \mod \left( \left\lfloor \frac{y}{17} \right\rfloor 2^{-17\lfloor x \rfloor - \mod(\lfloor y \rfloor, 17)} \right), 2\right\rfloor.

The graph of this inequality is comprises every possible arrangement of black and white (1×1) squares that can be fit in a 106×17 grid. The difficult thing is that you need to locate the 106-by-17 box that contains the thing you want.

For example, my name (Petch Puttichai) appears at 0 \leq x \leq 106 and k \leq y \leq k + 17, where k is 32922520572696913382451905912623623647167183726429121431754312885129411666885193915949745564208638847962779004960137820128309880253556326299620426051843316781711466694127750198822966039318977833943222930199125709567725963414828291187020468933092013936070802306399352123884523508901675580302517101305664361846330981066146182280532463873220739993581702910381088258207784043222527183537656464346321232788544747517684361869138095386938096713005390871951618586863662892224485886579202764210376205132486407529459098019294538104832.

16143619_10211226477115213_293112715850431983_oI used the tool available at to find out the value k I want. You just need to draw the pattern that you want to locate on the graph, then the program will calculate the corresponding k.

If you now Python (a programming language), you can use this code snippet to plot out the 106×17 box given a value k.