Tsort's Constant

This is a mathematical rule which is probably as significant to Disc mathematics, physics and cosmology as Pi is to ours. It is formulated thus:

1.67563, or precisely 1,237.98712567 times the difference between the distance to the sun and the weight of a small orange.

Interestingly, the Tsortean Constant is being used now in certain informal schools of Roundworld mathematics, and is referenced on the Disc as a quote in accepted use.