[neitsa]

> Using the stars as a reference, Maskelyne’s team found that the plumb lines on either side of the mountain pointed just 0.0152 degrees apart.

I'm really interested in knowing how they could get such a precise measurement (even accounting for errors), especially in the field (outdoor). There's no figure depicting the apparatus they used, I wonder how it looked like.

Sometimes, I just ponder at how ignorant I am. If I was tasked with the same assignment, I'd definitely fail and this was performed 250 ago!

[throwway120385]

Maybe something similar to a vernier caliper.

From Wikipedia:

> The first caliper with a secondary scale, which contributed extra precision, was invented in 1631 by the French mathematician Pierre Vernier (1580–1637).[1] Its use was described in detail in English in Navigatio Britannica (1750) by mathematician and historian John Barrow.[2] While calipers are the most typical use of vernier scales today, they were originally developed for angle-measuring instruments such as astronomical quadrants.

https://en.wikipedia.org/wiki/Vernier_scale

So it would have been a contemporaneous technique with that initial angle measurement, and the use of a Vernier scale for angular measurements would have itself been common.

[ahazred8ta]

They had a vertical 'Zenith Telescope' that looked at the same star from two locations. They measured how far from vertical it shifted in the magnified field of view. https://en.wikipedia.org/wiki/Ramsden_surveying_instruments#... Similar instrumends measured the wobble of the Earth's axis. https://en.wikipedia.org/wiki/International_Latitude_Service