Let $X \hookrightarrow \mathbb R^d$ where $d$ is minimal (that is, $X \not \hookrightarrow \mathbb R^{d-1}$). When $X$ is the $(d-1)$-sphere, then the cone of $X$ still embeds into $\mathbb R^d$.
Are there any other manifolds $X$ which have this property?
(Related is Embeddability of the cone of Klein bottle to $\mathbb R^4$, where $X$ is the Klein Bottle)