Feyn may be used to produce relatively simple Feynman diagrams
within equations in a LaTeX document. While the feynmf package
is good at drawing large diagrams for figures, the present
package and its fonts allow diagrams within equations or text,
at a matching size. The fonts are distributed as Metafont
source, and macros for their use are also provided.

Homepage:
https://ctan.org/pkg/feyn
