With three fourths Purusha rose up: one fourth of him
again was here.
Thence he moved forth to every side over what eats not
and what eats.
Ralph T. H. Griffith
The surface that matched
Both passages fold to the same comparison surface. Accents, word breaks and sandhi are removed before comparison, so this string is not how either text reads.
These links are derived by comparing normalised Sanskrit surfaces. They show that two collections carry the same wording. They are not, by themselves, a demonstrated line of transmission between them, and the direction stored on an edge is a property of how it was built.
Rigveda is one of four collections held here. Cross-corpus comparison bottoms out at the weakest shared surface, because a Devanagari text and a romanised text share no code points.
How these were derived1
Parallelism is symmetric and this graph stores it as a directed edge, so these relations are traversed in both directions and each row states which way the stored edge ran. All 1,684 REUSES_TEXT_FROM edges point Samaveda-to-Rigveda, and 1,421 Rigvedic passages have reuse edges only inbound; following the arrow would show those 1,421 verses no reuse at all.