Weight Illusion

Here's a demonstration of an interesting weight illusion.

   

Here is an article on what I'm sure is the principle behind the demonstration above. 

Here are some marketed versions of the effect:

Heavy Handed

Less is More

Rav Arora's critiques of systemic racism

 NYPost: The fallacy of white privilege — and how it’s corroding society

Quillette: A Peculiar Kind of Racist Patriarchy

Grid Illusions

A grid illusion is any kind of grid that deceives a person's vision. The two most common types of grid illusions are Scintillating grid illusions and Hermann grid illusions.

Hermann Grid Illusion

The Hermann grid illusion is an optical illusion reported by Ludimar Hermann in 1870. The illusion is characterized by "ghostlike" grey blobs perceived at the intersections of a white (or light-colored) grid on a black background.

Scintillating Grid Illusion

The scintillating grid illusion is an optical illusion, discovered by E. and B. Lingelbach and M. Schrauf in 1994. It is often considered a variation of the Hermann grid illusion but possesses different properties.

It is constructed by superimposing white discs on the intersections of orthogonal gray bars on a black background. Dark dots seem to appear and disappear rapidly at random intersections, hence the label "scintillating". When a person keeps his or her eyes directly on a single intersection, the dark dot does not appear. The dark dots disappear if one is too close to or too far from the image.

Wikipedia: Grid Illusion

Grey Line Turns Blue

Focus on the black dot on the lower right and the moving grey stripe will turn blue. 

Thatcher Effect Video: Adele, Kanye West, Obama

 

Motion Aftereffect Illusion

 

Necker Cube Illusions

The Necker cube is an optical illusion named after Swiss crystallographer Louis Albert Necker (1832) which consists of a two dimensional representation of a three dimensional wire frame cube. 

It is an ambiguous figure in that it can be interpreted as having the front of the box facing downward or facing upward. This is due to the way in which the cube is drawn. When the edge lines cross, the picture does not show which is in front and which is behind. This ambiguity allows the viewer to interpret the cube's orientation either way. When staring at the image it may flip back and forth between these two orientations. 

Image Credit Alec Nevala-Lee

The version below is an interesting variation which is easily seen as a 2 dimensional figure as well as a 3 dimensional figure with two interpretations.

Illusions Index: Necker Cube
The Eye's Mind

Research Gate: Fruit flies are multistable geniuses: Necker cube figure

Is he going up or down the stairs?