The 9-sided Enneahedron

Christian Lawson-Perfect on creating the Herschel Enneahedron.

See the free trial from episode sponsor Brilliant - https://brilliant.org/numberphile

Christian at Newcastle University - https://www.staff.ncl.ac.uk/christian.perfect/

And mathstodon at https://mathstodon.xyz/@christianp

Christian's blog post about this - https://aperiodical.com/2013/10/an-enneahedron-for-herschel/

3D printable enneahedron on thingiverse at https://www.thingiverse.com/thing:248603

More interesting Numberphile videos:
Dodecahedrons - https://youtu.be/G9_l8QASobI
Higher Dimensional Shapes - https://youtu.be/2s4TqVAbfz4
Tetrahedral Boat - https://youtu.be/-IjGexS1T8U