diff --git a/examples/moi.py b/examples/moi.py
new file mode 100644
index 0000000..9ce17c1
--- /dev/null
+++ b/examples/moi.py
@@ -0,0 +1,11 @@
+"""
+Computes the moment of inertia for the mystery object
+"""
+import numpy as N
+import cadquery as Cq
+import nhf.primitive
+
+if __name__ == '__main__':
+    obj = nhf.primitive.mystery()
+    mat = N.array(Cq.Shape.matrixOfInertia(obj.val()))
+    print(mat)
diff --git a/nhf/primitive.py b/nhf/primitive.py
new file mode 100644
index 0000000..ac9209c
--- /dev/null
+++ b/nhf/primitive.py
@@ -0,0 +1,4 @@
+import cadquery
+
+def mystery():
+    return cadquery.Workplane().box(10, 5, 5)
diff --git a/poetry.lock b/poetry.lock
index db47204..69302dd 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -857,4 +857,4 @@ files = [
 [metadata]
 lock-version = "2.0"
 python-versions = "^3.10"
-content-hash = "172a6b2578a05dce25e7ea5c38b6f5217a23b3aa7f91e0ce5ea768a3d6090751"
+content-hash = "caf46b526858dbf2960b0204782140ad072d96f7b3f161ac7e9db0d9b709b25a"
diff --git a/pyproject.toml b/pyproject.toml
index 4608771..3431c0e 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -9,6 +9,7 @@ readme = "README.md"
 python = "^3.10"
 cadquery = "^2.4.0"
 build123d = "^0.5.0"
+numpy = "^1.26.4"
 
 [build-system]
 requires = ["poetry-core"]