Yesterday I found a book - I think by Lillian Too - that said that all multiples of the standard imperial foot plus auspicious lengths of the ruler where auspicious. Still - one has to wonder - one book is not enough.
Yes, I confirm that what Lillian Too says is correct. A Feng Shui foot is = to an imperial foot. If we use this exact length which is 43 cm or approximately 17 inches long, as the diagonal of a square, it is what Mathematicians call the `Magic or golden square'.
The Feng Shui foot repeats itself every 43 cm. I had written a short article on this in the past at this url: ../fs/ruler.htm
Center for Feng Shui Research