diff --git a/packages/cultmath/docs/design.md b/packages/cultmath/docs/design.md
index 01119faf..24e94c2c 100644
--- a/packages/cultmath/docs/design.md
+++ b/packages/cultmath/docs/design.md
@@ -360,8 +360,8 @@ together, laid out as `float4(gradient.xyz, value.w)`, with no value-only twin
   `simplexnoise1234` order (x over y, y over z, x over z), a total order, so the
   four corners are always a simplex. Upstream's `step` compares are cyclic: where
   the three components are equal, which includes the origin and every
-  `(t, t, t)`, the corners repeat the origin vertex and the value jumps by up to
-  0.77. `NoiseGradTests.SnoiseIsContinuousOnTheSimplexDiagonal` pins the order.
+  `(t, t, t)`, the corners repeat the origin vertex and the value jumps by about
+  0.77 near the origin and up to 1.56 at magnitudes of 64 and above. `NoiseGradTests.SnoiseIsContinuousOnTheSimplexDiagonal` pins the order.
 - `snoise_grad(float3 p)` carries `snoise(float3)` to value-and-gradient form,
   following the differentiation in webgl-noise `src/noise3Dgrad.glsl` (Ashima
   Arts / Ian McEwan, MIT), which uses the same radius, permutation and scale as
diff --git a/packages/cultmath/tests/CultMath.Tests/NoiseGradTests.cs b/packages/cultmath/tests/CultMath.Tests/NoiseGradTests.cs
index f55cf38e..153886db 100644
--- a/packages/cultmath/tests/CultMath.Tests/NoiseGradTests.cs
+++ b/packages/cultmath/tests/CultMath.Tests/NoiseGradTests.cs
@@ -192,7 +192,8 @@ public sealed class NoiseGradTests
 
     // The simplex diagonals are where x0's three components compare equal. The tie rule must be a total
     // order there (math.snoise): with a cyclic or all-strict compare the four corners stop being a
-    // simplex and the value jumps by up to 0.77 on the line (t, t, t), lattice diagonals included.
+    // simplex and the value jumps on the line (t, t, t), lattice diagonals included: about 0.77 near the
+    // origin, up to 1.56 at magnitudes of 64 and above.
     [Fact]
     public void SnoiseIsContinuousOnTheSimplexDiagonal()
     {