How did Fermi calculate the strength of first nuclear explosion?

[bksree]

Hi
There is a story that Enrico Fermi calculated the intensity of the first nuclear test at Los Alamos from the distance moved by scraps of paper. Are there documented details of the calculation in any paper / book ?

TIA

 

[mfb]

Wikipedia has a reference to it:

http://www.lanl.gov/science/weapons_journal/wj_pubs/11nwj2-05.pdf