Tools of the trade: were early scientists and mathematicians really "writing with feathers using light from burning animal fat?"

Question

I've used the phrase more than once, but in this answer I wrote:

closing thoughts: Realistic orbits are not perfect conics, and so they and their Keplerian elements do not represent realistic orbits. They are only approximations to reality, and so are not right even though they are close.

Keplerian elements were used when people were writing with feathers using light from burning animal fat (if they were not busy being burned at the stake themselves). They are a mixed blessing in the 21st century when everything has so many more digits.

I understand that I am probably jumbling a few different centuries together there, but I am wondering about the hardware more than the politics.

In the fields of mathematics and orbital mechanics, say from Kepler to Lagrange, were mathematical derivations and computations done with pens made from feathers, and if an inspiration came after sundown, was light often as not produced by animal fat, whale oil, or the like?

Answer 1

Quick Internet search says that feather quills were mainly used in 600-1800 AD. After that people gradually switched to steel.

First true mathematicians (Babylonians) wrote on clay tablets. In the Greek/Roman Antiquity they wrote on papyrus, presumably with reed pens or brushes. Apparently they switched from brushes to pens in Ptolemaic Egypt, that is exactly when serious mathematics started:

https://www.brooklynmuseum.org/community/blogosphere/2010/09/22/pigments-and-inks-typically-used-on-papyrus/

Papyrus was used for "publication", for books and perhaps for letters, not for the actual work. The work was done on wax tablets, since the Roman times, and on sand before that. Even in 18th century, paper was not cheap enough for use as "scratch paper".

The data on when pencil became common diverge by 200 years, some say in 16th century, others in 18th.

Speaking of light sources, it does not have to be animal fat. The most common lamps used all kinds of vegetable oil. These lamps of various shapes were commonly used since Paleolith till 20th century in many places. In many locations, vegetable oil is cheaper than animal fat or wax candles.