Maaseh Rav Siman 13
Can copy this into an AI, or connect the whole library to your assistant. For deeper learning, you can directly use the original seforim, sites, and apps.
ציצית י"ב אגודלין, וגדיל שליש. היינו כל פרשה רוחב אצבע אגודל:
Sefaria Community Translation
Tzitzit should be 12 thumbs-width long, and the wrapped/knotted portion one third (of this total, so 4 thumbs-widths). Each wrapped portion was one thumb-width.