Ambiguous Optical Illusions

A very famous illusion - young lady or old hag?

In 1915, a cartoonist named W.E. Hill first published this drawing. It's hard to see what it's supposed to be. Is it a drawing of a pretty young girl looking away from us? Or is it an older woman looking down at the floor? Well, it's both. The key is perception and what you expect to see. Here's a hint: The young girl's necklace is the older woman's mouth. The young girl's chin and jaw are the older woman's nose.

Is it a man playing a saxophone, or a girl's face?

A wine goblet - or two faces in profile?

The white triangle looks very real, although there's no triangle per se.