وقال أبو يوسف فيما لا يوسق كالزعفران والقطن يجب فيه العشر إذا بلغت قيمته خمسة أوسق من أدنى ما يدخل تحت الوسق
Translation: Abu Yusuf says that for non-wasq-measured goods such as saffron and cotton, ushr is due when their value reaches the value of five awsuq of the least-valued comparable wasq-measured produce.
For goods not traditionally reckoned in awsuq, Abu Yusuf uses a valuation comparison: compare their value with five awsuq of the least-valued produce to which that measure applies.
His test is a price threshold, not a claim that cotton or saffron has the same physical bulk as that grain.