Saltire detected the symbol, which often appears with balls in the quadrants formed by the arms of the chi-cross, in standards that appear on the coins of Persepolis. She suggested that early Christians endorsed its solar symbolism as appropriate to Christ. She also wrote: "although it cannot be proved, ... in the white saltire of St. Andrew we still have a reminiscence of the old standard of the Persepolitan kingdom". In the old European Union standard, a black saltire set in an orange square is the hazard symbol for irritants (Xi) or harmful chemicals (Xn). It indicates a hazard less severe
Square packing in a square Square packing in a square Square packing in a square is a packing problem where the objective is to determine how many squares of side 1 (unit squares) can be packed into a square of side "a". If "a" is an integer, the answer is "a", but the precise, or even asymptotic, amount of wasted space for non-integer "a" is an open question. The smallest value of "a" that allows the packing of "n" unit squares is known when "n" is a perfect square (in which case it is ), as well as for "n" = 2, 3, 5, 6,