[cben]

I learnt this from Concrete Mathematics (Graham, Knuth, Patashnik). Don't remember if main text or the side notes of accumulated student wisdom... (I dont mean on my copy, this textbook is _printed_ with tons of amusing/insightful side notes)

They also mention _approximate_ cm/inch conversion is doable by double shift on the Fibonacci scale - if golden ratio was exactly 1.6, its square would be 2.56, but actual phi² = 2.618 which is quite bad approximation for 2.54...