Slide Rules
osgalleries.org
osgalleries.org
They are low-tech, continuous (vs. discrete, as in "tables with values in a booklet") lookup "tables" for functions that would have been too time-consuming (or error-prone?) to compute at "runtime". And they even allow parameters to be taken into account.
These things are absolutely ingenious inventions.
I find it quite handy in daily use, for example converting between Celsius and Fahrenheit, kilometers and miles, and currency conversions when traveling. I'll even use it sometimes when calculating a tip (the F<->C conversion of 1.8 conveniently aligns with a typical tip of 18%).
Explanations on slide rules:
https://www.math.utah.edu/~alfeld/sliderules/
A "slide rule creator" program that allows you to generate slide rules for arbitrary functions that are computable with slide rules:
My wife may have had one, though she would have called it a "proportion wheel"--people doing print production used these well into the 1980s and perhaps beyond to calculate the reduction need to make photographs fit on a page.
In my view, the great think about slide rules is that they do not encourage false precision. Too many calculator users will copy all those decimal points without considering how far they are meaningful.
This is by far the biggest loss from leaving the slide rule behind. People now confuse a greater amount of data with having more information. We have generations who believe they're being more accurate because they appear have greater precision, but in reality they're just more confident in their innumeracy.
Hearing more lies (as in the the extra digits) doesn't make you more right. This truth does not just apply to arithmetic, but at least it's more measurable with numbers.
One thing I've learned over the decades is it often benefits the craftsman to use a specific tool for a specific job. Sometimes a general-purpose digital computer is not the most appropriate tool when a simple hand-held analog device will give you the right answer every time without batteries or reception, in the rain or damp or cold.
I learned to use a slide rule as a youth because it was an important part of the high school science curriculum (how else were you going to calculate all those Ksp values in chemistry? Long hand?). I also have a pile of them I've collected over the years. Long may they, uh, rule.
A lot of them are sponsored or provided by corporations or trade associations, TRW provided the ICBM Effectiveness & Survivability model which looks really useful:
https://osgalleries.org/collectors/davis/info_and_image.cgi?...
Even more handy would be the Ground Zero/Bomb Damage slide rule:
https://osgalleries.org/collectors/davis/info_and_image.cgi?...
This is an outstanding black slide rule and its maker has remained anonymous, it's pretty dark but I guess a bright enough flash of light is expected to be available when you need to do this calculation.
There are more of them on that site.
If you have a series of numbers you want to scale by a known fraction, you can just set the slide rule so that the numbers in the fraction are over and under each other, then leave it there and even a two-year old can read off scaled numbers like it's nobody's business.
What does this have to do with the kitchen? The recipe calls for 50 g of butter, but you want to make as much as possible and you are constrained by owning 85 g of butter. Set slide rule to 85/50, then read all other ingredient amounts off the slide rule, scaled by the same amount.
Unfortunately, there are no scales on it for "evaporation" and "shitty construction", or the Aral Sea[2] might still be there.
[1] https://osgalleries.org/collectors/davis/info_and_image.cgi?...