Shiva Purana
यथा यथा लघुः स्याद्वै तथाधिकफलप्रदम् । एकैकतः फलं प्रोक्तं दशांशैरधिकं बुधैः १८ ।
The lighter the Rudrākṣa, the more fruitful it is. Each of these is fruitful and that of a weight of one tenth is considered by scholars as the most fruitful.
english translation
yathA yathA laghuH syAdvai tathAdhikaphalapradam । ekaikataH phalaM proktaM dazAMzairadhikaM budhaiH 18 ।
hk transliteration by Sanscript