> sticking their thumb over one end of a straw dipped in the liquid

Brings back memories of learning how to do that with my siblings. Every chance we got, we would scrunch up straw wrappers and then use the method to animate the wrapper with liquid.

Not certain if I should show my kids how to do that.

The pipettes I worked with in school 30 years ago were effectively glass straws with a mark for the designated volume. One dipped it in the solution over the mark, used the thumb to seal it, and then carefully let tiny amounts of air in to drop the bottom of the miniscus down to the line.

It was terrible and nothing ever worked and my thumbs hurt.

One of the first medical instruments I developed code for featured automated precision pipettes (precision measured in single microliters) for sampling reagents and human body fluids.

We had a guest once who used to be a lab nurse and mentioned using mouth pipettes. The looks of horror on the scientists in the room was palpable!

A bit further back - https://en.wikipedia.org/wiki/Radium_dial

> Radium dials were typically painted by young women, who used to 'point' their brushes by licking and shaping the bristles prior to painting the fine lines and numbers on the dials. This practice resulted in the ingestion of radium, which caused serious jaw-bone degeneration and malignancy and other dental diseases. The disease, radium-induced osteonecrosis, was recognized as an occupational disease in 1925 after a group of radium painters, known as the Radium Girls, from the United States Radium Corporation sued. By 1930, all dial painters stopped pointing their brushes by mouth. Stopping this practice drastically reduced the amount of radium ingested and therefore, the incidence of malignancy.