| c = 1 | This user uses natural units. |
The default setting for this userbox is to set c=1, thus measurements are all relative to the speed of light, which is actually how we do it now, except c=299792458 instead. Of course, there are many different types of natural units, so in using this template you can set whatever you want =1, using the following code:
{{ User:SamuelRiv/Userboxes/natural | [[Boltzmann's constant|{{math|''k''<sub>''B''</sub>}}]] | 12}}
This generates a userbox like the one seen on my main page, with kB=1 instead. So basically you can set any fundamental constant you want =1 (except electron mass, because that's just stupid).